Transmission
n Compon
nent Overrview
The
e typical Allison
A
four speed uses
u
a serries of sha
afts to tran
nsmit rota
ational pow
wer.
A. The
T turbin
ne shaft is
s at the fro
ont of the transmisssion in yellow.
1. Itt transmitss rotationa
al power from
f
the torque
t
con
nverter turbine to th
he transm
mission
gea
aring.
B. The
T groun
nd sleeve in white iss often referred to as
a the sta
ator shaft.
1. The
T torque
e converte
er stator splines
s
to the groun
nd sleeve..
C. The
T main shaft in blue
b
is in the middle
e of the tra
ansmissio
on.
1. Itt transmitss rotationa
al power from
f
the turbine
t
sh
haft to inte
ernal comp
ponents.
D. The
T sun gear
g
shaft in brown is positioned aroun
nd the ma
ain shaft.
1. Itt transmitss rotationa
al power from
f
the turbine
t
sh
haft to inte
ernal comp
ponents.
E. The
T outpu
ut shaft is in green at
a the rear of the tra
ansmissio
on.
1. Itt providess transmis
ssion outp
put to the vehicle's
v
d
drive
train
n.
The
e transmisssion's shafts are supported in the hou
using by:
A. The
T front support.
s
1. Bolted
B
to the
t transm
mission ho
ousing and
d supportts the turb
bine shaft..
B. The
T Centrre supportt.
C. The
T rear cover.
c
1. Supports
S
t outputt shaft.
the
The
e torque converter
c
is
i located at the fro
ont of the transmiss
t
sion.
A. It suppliess rotationa
al input fro
om the engine to th
he transmiission turb
bine shaftt.
The
e typical Allison
A
four speed has
h three sets
s
of pla
anetary ge
ears.
A. The
T front, centre an
nd rear pla
anetary ge
ear sets.
1. Some
S
com
mponents are physically attacched to ea
ach otherr through the
t conne
ecting
drum.
Planetary gear compo
onents are
e held or input by cllutches.
A. The
T typica
al four spe
eed uses five
f
clutch
hes, labelled from the
t rear off the transsmission.
1. Clutches
C
I through 3 are statiionary clu
utches.
a. They
T
hold compone
ents.
2. Fourth
F
and
d forward clutches are rotatin
ng clutche
es.
a. They
T
conn
nect shafts
s to provid
de rotational input to
t variouss planetaryy gear
com
mponents..
Con
ntrol valve
es control clutch ap
pplication and relea
ase.
A. Control
C
va
alves are located
l
in
n the valve
e body assembly an
nd front support.
Torrque Convverter Ope
eration
The
e torque converter
c
provides
p
a hydro-m
mechanica
al coupling
g that sup
pplies rota
ational
inpu
ut from the engine to the tran
nsmission
n's gearing
g.
The
e torque converter
c
has
h four main
m
components:
A. The
T pump
p, stator, turbine and lock-up clutch.
The con
nverter's pump
p
is bolted to
the convverter covver.
A. The pump
p
rota
ates at en
ngine
speed.
1. As th
he pump ro
otates, flu
uid enters
from aro
ound the pump hub
b.
2. Centrrifugal forrce causess fluid to
be throw
wn around
d the outsside of the
e
pump and over to
o the convverter
turbine.
3. Once
e the force
e reaches a certain
point, th
he fluid be
egins to sp
pin the
turbine.
The con
nverter's turbine
t
is splined to
o
the tran
nsmission turbine sh
haft.
A. Fluid
d from the converter pump
strikes the
t turbine
e's vaness and
eventua
ally forcess the turbin
ne to
rotate.
l. Since the turbin
ne is splin
ned to the
turbine shaft, the
e turbine shaft
s
rotates and supp
plies input to the
transmission's ge
earing.
2. Fluid exits the turbine near its
hub
b and flow
ws to the stator.
s
The
e stator re
edirects flu
uid back to
o the convverter pum
mp.
A. When
W
fluid
d from the
e turbine hits
h the fro
ont of the stator bla
ades, the stator
s
lockks
aga
ainst its on
ne-way clu
utch.
1. Fluid
F
leaving the loc
cked stato
or is directted back to
t the pum
mp at an accelerate
a
ed rate,
incrreasing to
orque.
B. As
A the turb
bine gains
s speed, it
i directs oil
o to the back
b
side of the sta
ator blades,
cau
using the stator
s
to "ffreewheel."
1. Fluid
F
flowing throug
gh the free
ewheeling
g stator is no longerr accelera
ated and does
d
not
incrrease torq
que.
2. As
A turbine speed increases, flow
f
throu
ugh the stator beco
omes smoother and
d
eve
entually stops.
Vortexx Flow
Vortexx flow occu
urs when the stator
is in th
he locked position.
A. Fluid is directed from the
t pump
to the turbine.
1. The
e turbine iss still stalled or
moving
g slowly.
B. Fluid exiting the turbin
ne strikes
the fro
ont face off the stato
or blades.
1. Thiss locks the
e stator.
C. The
e locked stator
s
directs fluid
back to
o the pum
mp at an
accele
erated rate
e.
1. This
T
helpss the pump
p increase
e torque be
b adding an extra "push."
Rotaryy Flow
Rotaryy flow occurs when the
stator is in the frreewheeliing
positio
on.
A. As the
t turbine begins to
t rotate
and itss speed in
ncreases, the fluid
exiting
g the turbin
ne strikess the backk
of the stator blades.
1. Thiss frees the
e one-wayy clutch
and allows the stator
s
to ro
otate.
2. The
e fluid flow
w through the statorr
becom
mes much smoother and
slowly ceases.
a. Thiss eliminate
es torque increase.
Torrque Convverter Ope
eration
Locck-Up Cluttch Opera
ation
The
e torque converter's
c
s fluid cou
upling will never allo
ow turbine
e speed to
o equal en
ngine
spe
eed.
A. Once
O
rotary flow ha
as been achieved and
a certain
n speed and
a range
e requirem
ments are
mett, the torque converter attain
ns "lock-up
p."
1. This
T
physical conne
ection betw
ween the converterr turbine and
a pump
p allows th
he turbine
to ro
otate at engine spe
eed.
Lock-up clutch components include:
A. The backing plate - located directly in front of the turbine and bolted to the converter
front cover.
1. The backing plate always rotates at engine speed.
B. A lock-up clutch plate assembly - located next to the backing plate.
1. It's splined directly to the turbine shaft.
C. The lock-up clutch piston - located inside the converter front cover.
1. It's splined to the converter front cover and always rotates at engine speed.
Hydraulic fluid forced between the front cover and lock-up clutch piston causes the
piston to move.
A. This "sandwiches" the clutch plate between the piston and backing plate, forcing the
clutch plate to rotate at engine speed.
1. Since the clutch plate is splined to the turbine shaft, the transmission's input equals
engine RPM.
Planetary Ge
ears
Allisson transm
missions use sets of
o planeta
ary gears to
t create a variety of output ratios.
A. Understan
U
nding basic planeta
ary gear operation is critical to
t understtanding ba
asic
tran
nsmission operating
g principle
es.
B. Planetary
P
gear sets
s consist of
o a sun gear, plane
etary pinio
on gears (held
(
by a carrier)
and
d a ring ge
ear.
C. Gear
G
relattionships:
1. When
W
two gears witth externa
al teeth mesh, theirr rotation is opposite each other.
a. Example
E
- the sun gear
g
and pinion
p
gea
ars.
2. When
W
a ge
ear with external
e
te
eeth mesh
hes with a gear with
h internal teeth,
t
the
ey rotate
in th
he same direction.
d
a. Example
E
- the pinion gears and
a the rin
ng gear.
D. These
T
gea
ar relation
nships pro
ovide the basis
b
for planetary
p
gear operation.
The
e Basic law
ws Of Pla
anetary Ge
ear Sets
When one planetary componen
c
nt is held and
a anoth
her is rotatted, or "in
nput," the third
mem
mber becomes an output me
echanism.
A. Depending
D
g on whic
ch compon
nents are held and input, the
e planetarry gear se
et can
devvelop vario
ous outpu
ut ratios:
. De
ecrease output
o
spe
eed.
. Inccrease ou
utput spee
ed.
. Prrovide dire
ect, 1 to I drive.
. Crreate reve
erse.
B. To
T decrea
ase speed
d:
1. The
T ring gear is held and the
e sun gearr is rotated
d, or "inpu
ut."
a. The
T carrier become
es output, rotating at
a a slowe
er speed th
han the su
un gear.
C. To
T increasse speed::
1. The
T ring iss held and
d the carrier is input.
a. The
T sun gear becom
mes outpu
ut and rota
ates faste
er than the
e carrier.
D. In direct drive:
d
1. No
N compo
onents are
e held and
d two com
mponents are
a input in the sam
me directio
on and
spe
eed.
a. The
T third member
m
becomes
b
o
output
rotating the same spe
eed and direction
d
a input.
as
E. To
T create reverse:
1. The
T carrier is held and
a eitherr the sun or
o ring gear is inputt.
a. Iff the ring gear is input, the sun gear becomes
b
o
output.
1) The
T sun gear rotate
es the opp
posite dire
ection, fasster than the ring ge
ear.
b. Iff the sun gear
g
is inp
put, the ring gear becomes
b
o
output.
1) The
T ring gear
g
rotate
es the opp
posite dire
ection, slo
ower than the sun gear.
g
Clutches
Clutches provide the input and holding power plan
netary gea
ar sets req
quire for operation.
o
.
A. Clutches
C
c be eitther rotatin
can
ng or stationary.
1. Rotating
R
c
clutches
su
upply rota
ational inp
put to othe
er shafts or
o compon
nents.
2. Stationary
S
y clutches hold com
mponents in
i place, allowing
a
o
other
components to be
inpu
ut and outtput.
B. Clutches
C
c
consist
of two interttwined se
ets of clutcch plates and
a a pistton.
1. Two
T
kinds of plates are used
d - fibre, "ffriction," plates
p
and steel, "re
eaction," plates.
p
a. Plates
P
are alternate
ed in the clutch
c
asse
embly so that they sandwich
h each oth
her.
C. One
O set of clutch plates is sp
plined to an
a inner componen
c
nt, the othe
er is splined to an
oute
er component (usually a hou
using).
D. Even
E
thou
ugh the pla
ates are intertwined
d, they rotate indep
pendentlyy.
E. The
T clutch
h assembly has a piston
p
and
d spring.
1. When
W
the clutch is applied,
a
th
he piston forces the
e intertwin
ned platess togetherr as one
unitt.
the piston
2. When
W
the clutch is released,
r
n is return
ned by the
e spring.
F. Iff one of th
he compo
onents splined to the clutch plates
p
is stationary, the clutch is a
"sta
ationary cllutch."
G. If
I both com
mponents
s splined to
t the cluttch plates are capa
able of rota
ating, the clutch is
a "rrotating clu
utch."
Transmission
n Configuration
The
e typical fo
our speed
d on-highw
way transm
mission uses three
e planetaryy gear setts.
A. They
T
are labelled
l
re
ear, Centrre and fro
ont from th
he back off the transsmission.
The
e four speed on-hig
ghway tran
nsmission
n uses five
e clutchess.
A. They
T
are labelled
l
1st through
h 4th and forward, from the back
b
of th
he transmission.
1. When
W
the forward clutch
c
is applied, it connects
c
the turbin
ne shaft to
o the main
n shaft.
2. When
W
4th clutch is applied,
a
itt connectss the turbiine shaft to
t the sun
n gear sha
aft.
3. When
W
3rd clutch is applied,
a
itt holds the
e sun gea
ar shaft sta
ationary.
4. When
W
2nd
d clutch is applied, it
i holds the front pla
anetary ca
arrier.
5. When
W
1st clutch is applied,
a
itt holds the
e rear plan
netary ring
g gear.
Varrious planetary gea
ar set com
mponents are
a conne
ected via shafts
s
and
d the conn
necting
drum.
Clutches provide rotattional inpu
ut and holding powe
er to crea
ate a varie
ety of ratio
os.
Pow
wer Flowss
Neu
utral
When the tra
ansmission is in neu
utral, the only
o
clutcch applied is 1st.
A. 1st
1 clutch holds the
e rear ring gear.
B. Since
S
no other
o
clutc
ches are applied,
a
n power is
no
i transmitted throu
ugh the
tran
nsmission gearing (it
( takes tw
wo applied
d clutchess to transm
mit powerr).
Firsst Range
When the tra
ansmission is in firsst range, the 1st and forward clutches are applie
ed.
A. Clockwise
C
e rotation from
f
the turbine
t
sh
haft is dire
ected to th
he main sh
haft throug
gh the
forw
ward clutcch.
B. This
T
powe
er is transmitted to the
t rear planetary
p
s gear.
sun
C. Since
S
the rear planetary ring
g gear is held
h
by 1st clutch, and
a the re
ear sun ge
ear is
inpu
ut clockwiise, the re
ear carrierr becomess clockwisse output – and it's connecte
ed to the
outp
put shaft.
Seccond Rang
ge
In second
s
ran
nge, forwa
ard and2n
nd clutche
es are app
plied.
A. The
T forwa
ard clutch locks the turbine shaft to the
e main shaft so they both rottate
clocckwise.
B. The
T Centrre planeta
ary ring ge
ears spline
ed to the main
m
shafft, so it rottates clocckwise,
too..
C. The
T front planetary carrier is held by 2nd
2 clutch
h.
D. The
T Centrre carrier is splined
d to the rea
ar carrier which is splined
s
to
o the outpu
ut shaft.
T Centrre ring gea
ar is inputt at a rate of speed that overrcomes th
he carrier, causing
E. The
the carrier to act as a held mem
mber.
F. The
T resultt is the Ce
entre sun gear rotatting in the
e opposite
e direction
n, or countterclocckwise
G. Since
S
the Centre and front sun gears are spline
ed to the sun
s gear shaft, the front sun
n
gea
ar become
es counter-clockwisse input to
o the frontt planetaryy.
H. The
T countter-clockw
wise input and the held
h
carrie
er cause a clockwisse output at the
fron
nt ring gea
ar.
I. The front riing gear transmits this
t
clockw
wise power through
h the conn
necting drrum, to
the rear carriier, which is splined
d to the ou
utput shafft.
Thirrd Range
In th
hird range
e, the forw
ward and 3rd
3 clutch
hes are ap
pplied.
A. Turbine
T
sh
haft powe
er is transm
mitted thro
ough forw
ward clutch
h to the main
m
shaft.
B. 3rd
3 clutch holds the
e sun gear shaft sta
ationary.
C. The
T main shaft is splined to the
t Centrre planetary ring ge
ear, causin
ng it to rottate
clocckwise.
D. The
T Centrre planeta
ary sun ge
ear is splin
ned to the
e sun gearr shaft, an
nd is held
stattionary byy 3rd clutc
ch.
E. The
T resultt is clockw
wise outpu
ut at the Centre
C
planetary ca
arrier.
F. Centre
C
pla
anetary ca
arrier transsmits clocckwise rottation thro
ough the connecting
c
g drum,
to th
he rear ca
arrier, which is splin
ned to the
e output sh
haft.
Fou
urth Range
Forw
rward and 4th clutches are applied wh
hen the tra
ansmissio
on is in fou
urth range
e.
A. The
T main shaft and
d turbine shaft
s
are both
b
rotatiing clockw
wise throu
ugh forwarrd clutch.
B. 4th
4 clutch transmits
s the same
e rotating power to the sun gear
g
shaftt.
C. The
T Centrre planeta
ary ring ge
ear and Centre plan
netary sun
n gear are
e both rota
ating at
the same spe
eed.
D. This
T
causes the Ce
entre planetary carrrier to rota
ate at the same spe
eed, too.
E. The
T Centrre planeta
ary carrier is splined
d to the co
onnecting drum, wh
hich transsmits
pow
wer throug
gh the rea
ar carrier to
t the outp
put shaft.
Revverse
Revverse is th
he only "m
moving" ge
ear that do
oesn't req
quire forwa
ard clutch
h. 4th and 1st
cluttches are applied.
A. Applying
A
4 clutch causes th
4th
he sun ge
ear shaft to rotate clockwise.
c
B. The
T sun gear
g
shaft splines to
o the frontt and Cen
ntre sun ge
ears, so they are ro
otating
clocckwise.
C. The
T Centrre sun gea
ar's input speed ovvercomes the carrie
er speed, causing th
he carrierr
to act
a as a he
eld memb
ber.
D. This
T
causes the Ce
entre ring gear to ro
otate coun
nter-clockw
wise.
E. The
T Centrre ring gea
ar is splined to the main sha
aft, causing it to rota
ate counte
erclocckwise.
F. The
T main shaft is also splined to the re
ear planettary sun gear
g
- it ro
otates cou
unterclocckwise an
nd become
es the inp
put for the rear plan
netary.
G. 1st
1 clutch holds the
e rear ring
g gear stattionary, ca
ausing the
e rear carrrier to beccome
outp
put - it rottates coun
nter-clockw
wise, causing the output
o
sha
aft to rotatte counterclocckwise.
HYDRAULIC SYSTEM
Hydraulics
The hydraulic system generates, directs and controls the pressure and flow of
hydraulic fluid in the transmission.
A. Oil is directed through valves, circuits and orifices.
B. Pressurized oil controls clutch application, lubrication and cooling.
C. On-highway and off-highway systems are configured differently, but operate on the
same principles.
The hydraulic system is a "closed loop."
A. Fluid travel begins in the sump, travels throughout the system to perform various
tasks, then returns to the sump to cycle through again.
On-Highway Hydraulics Overview
On-highway control valves are located in the valve body and front support.
Hyd
draulic con
ntrol overrview
A. Hydraulic
H
flow is initiated by the charg
ging pump
p, which iss driven byy the torque
con
nverter pump.
1. Itt always rotates
r
at engine sp
peed.
B. Pressure
P
f
flows
from
m the pum
mp to the main
m
pressure regu
ulator.
1. Pressure
P
f
flows
through an orrifice to the top of th
he valve to
t regulate
e main pre
essure.
2. Main
M
presssure is dirrected to various
v
co
omponentts.
3. Exhausted
E
d main pre
essure charges the
e torque co
onverter circuit.
c
C. Shifting
S
is primarily controlled
d by a series of casscading shift
s
signal valves and
a relay
valvves.
1. When
W
the transmiss
sion is rea
ady to shifft, the shifft signal valves provvide a ma
ain
presssure sign
nal to theiir correspo
onding re
elay valvess.
D. Governor
G
and modulator pre
essure work togethe
er to posittion the sh
hift signal valves.
pressure is directed to the bottom
1. Governor
G
b
of each
e
shiftt signal va
alve.
a. As
A output speed inc
creases, the govern
nor spins faster, inccreasing governor
g
p
pressure.
2. Modulator
M
pressure
e is directe
ed to the top
t of eacch shift sig
gnal valve
e.
a. Modulator
M
pressure
e increases and deccreases based on throttle
t
po
osition - ass the
thro
ottle is ope
ened, mod
dulator prressure de
ecreases.
pressure starts pusshing the shift signal valve
E. As
A the veh
hicle gains
s speed, governor
g
up against
a
sp
pring pres
ssure.
1. Modulator
M
pressure
e acts as an
a assist when
w
the throttle iss depresse
ed.
F. once
o
the shift
s
signa
al valve mo
oves up, main presssure flow
ws to the relay valve
e.
T
pushe
es the rela
ay valve down,
d
exh
hausting th
he applied
d clutch and
a allowin
ng main
1. This
presssure into
o the onco
oming cluttch apply circuit.
On-Highway Hydraulics
Overview
Trimmer valves located in the
clutch apply circuit regulate
oncoming clutch application.
A. Full throttle shifts result in
firm clutch apply.
B. Partial throttle shifts result in
smooth clutch apply.
C. Trimmer valves consist of an
orificed trimmer at the top, a
plug in the middle and a spring
and stop at the bottom.
1. As the clutch apply circuit fills, pressure is fed to the top of the trimmer valve.
2. Initially, this forces the trimmer and plug down against spring and fluid pressures.
a. This allows clutch apply pressure to exhaust slightly, regulating oncoming clutch
application.
b. Main pressure flows through the orifice in the trimmer and begins forcing the plug
down.
c. Once the plug bottoms, pressure forces the trimmer up, blocking the clutch apply
circuit's exhaust passage and fully applying the clutch.
The amount of fluid pressure under the trimmer plug is controlled by the trimmer
regulator.
A. Trimmer regulator relies on modulator pressure for positioning.
1. During closed or partial throttle operation, modulator pressure is high and lifts
trimmer regulator off its seat.
a. This blocks the main pressure feed passage, exhausting the pressure at the bottom
of the trimmer valves, resulting in soft, easy shifts.
2. During full or nearly full throttle, the trimmer regulator stays down on its seat.
a. This opens the pressure feed to the bottom of the trimmers and results in quick, firm
clutch application.
Module Review Questions
l. What is the torque converter's purpose in a typical Allison transmission? (Check the
correct answer:
- A. To provide engine oil cooling when the vehicle is at idle.
_ B. Transmitting engine rotational power to the transmission gearing.
_ C. Providing a mechanical over-speed protection device for both the transmission
and the engine.
_ D. Restricting the flow of transmission oil to clutches and valves during downshifting
or when in neutral.
2.The three primary components of a torque converter are (check the correct answer):
- A. The turbine, rotor and Pump.
- B. The stator, turbine shaft and input shaft.
- C. The pump, stator and turbine.
- D. The front support, sun gear shaft and rear bushing'
3. Which of the following best describes the torque converter's operation? (Check the
correct answer.):
_ A. As the engine spins, the torque converter provides resistance - this resistance
builds hydraulic pressure which is directed to the transmission gearing and clutches.
_ B. The engine provides input to the torque converter stator which directs fluid to the
turbine shaft - once fluid reaches the turbine shaft, it's re-directed to the front pump.
_ C. The engine spins, driving the torque converter pump - the pump throws oil against
the turbine vanes, which rotates the turbine (which is splined to the turbine shaft).
4. When torque converter turbine speed approaches pump speed (check the correct
answer):
_ A. Oil flowing to the stator begins striking the opposite sides of the stator vanes, and
torque multiplication is stopped and a fluid coupling develops.
_ B. The torque converter senses an over-speed condition and immediately sets a
trouble code in the Electronic Control's ECU.
_ C. Oil flowing to the stator is now allowed to flow to the turbine shaft, itself, and the
turbine shaft spins as fluid hits the shaft's splines.
5. The torque converter's lockup clutch (check the correct answer):
_ A. Allows the torque converter to attain a one-to-one coupling.
_ B. Consists of a piston, clutch plate and cylinder.
_ C. Is controlled by a solenoid on the vehicle's engine.
_ D. Prevents high stall torque situations from damaging the engine or transmission.
6. Which of the following best describes lockup clutch operation? (Check the correct
answer.):
- A. As the engine reaches maximum RPM, the lockup clutch is applied, creating a
drag to reduce engine RPM and prevent engine damage.
- B. Clutch apply pressure compresses the lockup clutch plate between the piston and
back plate, locking all three components together.
- C. Main pressure fills the lockup clutch apply cylinder - the vanes on the lockup clutch
disc spin the disc and lock it to the back plate to create a mechanical connection.
7. The three components of a typical planetary gear set are (check the correct answer):
_ A. The front gear, side gears and ring gear.
_ B. The input gear, the pinion gears and the planetary gear.
_ C. The pinion gear, the carrier gear and the ring gear.
- D. The ring gear, pinions held by a carrier, and a sun gear.
8. Which statement best summarizes the Basic Laws of Planetary Gear Sets? (Check
the correct
answer.):
- A. When two components are held, the third component becomes an output unit.
- B. Holding one component and providing rotational input to the third unit allows the
held unit to begin spinning.
- C. When one component is held and another acts as input, the third becomes the
output mechanism.
- D. Holding two components and providing input to the third allows one of the two held
component to act as an output mechanism.
9. Clutches in the typical Allison transmission (check the correct answer):
_ A- Are not used because they tend to wear out.
_ B. Act to hold components or supply rotational input when required.
- C. Can be manually applied by the vehicle operator.
- D. Should be replaced every 50,000 miles or within three years, whichever come first.
10. Which of the following best describes power flow through a typical 4 speed
transmission when
Forward and 1st clutches are applied? (Check the correct answer):
_ A. Rotational power is supplied from the turbine shaft, through the Forward clutch
and to the sun gear shaft. The sun gear shaft rotates the Centre sun gear clockwise,
which turns the Centre ring gear counter-clockwise. This causes the Centre carrier to
turn clockwise, transmitting power through the connecting drum to the output shaft.
_ B. The turbine shaft spins the main shaft and the sun gear shaft. The front sun gear
turns counter-clockwise, causing the front ring gear to turn the connecting drum
clockwise. This turns the rear carrier and the output shaft clockwise.
_ C. Rotational power from the turbine shaft rotates the main shaft clockwise. This
turns the rear sun gear clockwise. The rear ring gear is held by 1st clutch, and the rear
carrier becomes output. This clockwise rotation is transmitted to the output shaft.
11. Which of the following best describes power flow through a typical 4 speed when
Forward and 3rd clutches are applied? (Check the correct answer):
_ A. Rotational power is transmitted from the turbine shaft to the main shaft through the
forward clutch. The sun gear shaft is held stationary by the third clutch. The Centre ring
gear is spinning clockwise, and the Centre sun gear is held stationary. The Centre
carrier provides clockwise rotation to the output shaft through the rear carrier.
_ B. The 3rd clutch holds the sun gear shaft stationary, holding the front sun gear
stationary. The main shaft receives rotational power from the turbine shaft through the
Forward clutch. This spins the rear ring gear clockwise, which forces the front carrier
clockwise. The front ring gear provides power to the output shaft through the rear
carrier.
_ C. The main shaft receives clockwise rotation from the turbine shaft through the
Forward clutch. This spins the rear sun gear clockwise. Since the sun gear shaft is
held in place by 3rd clutch, the rear ring gear is held stationary. This allows the rear
carrier to supply output to the output shaft.
12. What supplies the transmission with oil necessary for operation? (Check the
correct answer.):
_ A. The torque converter, driven by the engine.
- B. The main oil pump assembly, driven by the torque converter.
_ C. The front support assembly, which is rotated by the main oil pump drive assembly.
_ D. The converter pressure regulator and lockup clutch valves.
13. Governor pressure (check the correct answer):
_ A. Is created from main pressure, is based on engine output speed and signals the
torque converter when to apply the lockup clutch.
- B. Varies with output shaft speed and helps signal the appropriate valves regarding
upshifts, downshifts and converter lockup points.
_ C. Is based on engine RPM and does not vary much from actual main pressure.
14. Modulator pressure (check the correct answer):
- A. Is created by the modulator valve in the engine and controls the movement of
mechanical linkages that are usually connected to components in the vehicle's cab.
- B. Does not vary once the vehicle is moving and is used to signal valve body
components when the vehicle is coming to a stop.
- C. Is based on throttle movement and helps the transmission select shift points that
are applicable to the driving situation.
15. Which of the following statements about main, governor and modulator pressures
is true? (Check the correct answer.):
- A. Modulator pressure is high when the throttle is closed (at idle), governor pressure
increases as output shaft speed increases, and both pressures are main pressure that
has been changed.
- B. Modulator pressure is low when the throttle is wide open, governor pressure
decreases as output shaft speed increases, and main pressure varies based on
modulator and governor pressures.
- C. Modulator pressure is high when the throttle is open, governor pressure increases
as output shaft speed increases, and main pressure varies based on modulator
pressure, but isn't affected by governor pressure.
16. The shift valves in a non-electronically controlled transmission (check the correct
answer):
- A. Direct governor and modulator pressures to various valves and clutches in the
transmission to enable specific gear ranges.
- B. Move based on modulator and governor pressures and direct main pressure to the
appropriate relay valve.
- C. Rely only on main pressure for movement, direct governor pressure to the
governor pressure relief valve and feed the modulator valve.
17. Which of the following statements is not true? (Check the false statement.):
- A. Full throttle shifts occur later because modulator pressure is low and doesn't help
overcome the shift valve's spring pressure.
_ B. Downshifts occur more quickly as governor pressure decreases.
_ C. High modulator pressure allows earlier shifts.
- D. At full throttle, high modulator pressure and governor pressure both act to
overcome shift signal spring pressure.
18. Shift relay valves (check the correct answer):
- A. Are positioned by main pressure from the shift signal valves and direct main
pressure into clutch apply circuits.
- B. Act as shock absorbers for the transmission, reducing pressure to the clutch apply
circuits during initial application.
- C. Direct main pressure to the shift signal valves when the transmission is ready to
apply or release a clutch.
19. Trimmer valves (check the correct answer):
- A. Direct main pressure to the clutch apply circuits when the transmission is ready for
a shift.
- B. Prevent harsh shifts by reducing pressure to the clutch apply circuits during initial
clutch application.
_ C. Move based on modulator and governor pressures, and direct main pressure to
the appropriate shift relay valves.
ATE
EC - CEC
C System Overview
O
Allisson Transsmission Electronic
E
c Control System
S
prrovides th
he shifting "thought"" process
for Allison
A
tra
ansmissio
ons.
A. Electronic
E
c Control-e
equipped transmisssions use the same
e clutching
g and plan
netary
gea
ar compon
nents as convention
c
nal transm
missions.
1. The
T opera
ating princ
ciples are the same
e, but the Electronic
E
c Control uses
u
a dig
gital
elecctronic system to co
ontrol the transmission's hyd
draulics.
circuits
2.The Electro
onic Control uses an
a electro--hydraulicc valve bo
ody – the hydraulic
h
with
hin the ele
ectro-hydrraulic valvve body arre controlled by sollenoids.
3. These
T
sole
enoids tak
ke the pla
ace of conventional shift sign
nal valves, and are ultimatelyy
swittched "on" and "offf” by signa
als from th
he Electro
onic Contrrol Unit, orr "ECII."
The
e Electron
nic Control needs "ssensing" input.
A. Speed
S
sen
nsor inputt replacess governor pressure
e.
B. Throttle
T
po
osition sensor input replacess modulattor pressu
ure.
C. ECU
E
may also rece
eive input from temperature sensor
s
an
nd pressure switche
es.
D. System
S
m use pu
may
ush button
n or lever shift sele
ector.
E. System
S
co
ommunica
ates throu
ugh a serie
es of harn
nesses.
Electronic Control Applications
Several Allison transmissions are Electronically Controlled. The following on-highway
models are equipped with Electronic Control:
. MT(B) 648
. HT(B) 741
. HT(B) 748
. HTG) 755CR
. HT(B) 755DR
. V73l and VR731
The following off-highway models are equipped with Electronic Control:
. CLBT 5962and6062
. DP 8963
. CL(B)T 9681
. CLT 755 and CL(B)T 755
ON HIGHWAY APPLICATIONS
CITY DELIVERY
RUBBISH REMOVAL
OIL DELIVERY
SCHOOL BUS
TRANSIT MIXER
AIRPORT REFUELER
TRANSIT BUS
OVER THE ROAD TRACTORS
INNER-CIW BUS
DUMP TBUCK
TANK TRANSPORT
FIRE AND RESCUE
Electronic Control Unit
The ECU is an onboard microcomputer.
A. The ECU receives information through a wiring harness from a variety of sources.
l. The ECU uses this information to determine how and when shifts should occur,
B. There are three ECU types:
1. Splash Proof - earliest model, no longer in production.
2. Sealed Standard - replaced the Splash Proof.
3. sealed Plus II - has secondary mode capabilities and includes an additional
connector to accommodate a secondary shift selector and additional features.
ECU Mounting and Operation Concerns
The ECU should be mounted in an area protected from direct exposure to weather,
cleaning sprays, high concentrations of dust and sunlight.
A. Although the connectors and ECU body are "sealed," mount the unit in an area free
from road splash - don't allow the ECU to be immersed in water.
B. Mount the ECU in the coolest practical location with good ventilation.
C. Bolt the ECU to a metal structure to help dissipate the unit's heat.
D. Bolt the ECU securely to the vehicle's cab or chassis - position the connectors
"down" whenever possible to avoid direct moisture contact on the connectors.
E. Mount the ECU in a position that minimizes operator and technician/service
personnel contact - leave clearance to allow ECU connectors to be removed without
dismounting the unit.
F. Mount as close as possible to the battery power.
1. Long power leads result in voltage drops - keep the power leads short to help the
ECU meet voltage requirements.
The ECU's main power and ground inputs should be "dedicated" - no other electrical
component should share the ECU's power and ground inputs.
3. Voltage requirements vary with transmission temperature – a minimum of 10 volts is
required; 16 volts is maximum continuous voltage the system handles; 19 volts is the
maximum intermittent voltage the system allows.
G. In some situations, ECU power must be supplied by a dual power source (offhighway and emergency vehicle applications, and vehicles equipped with Jacobs
engine brakes).
1. An engine or transmission oil pressure switch and the master ignition switch should
both supply ECU power. This assures that power is supplied to the ECU under all
operating conditions.
H. The ECU requires continuous power for storing diagnostic codes and throttle sensor
calibration values.
l. This memory must be powered with 12 volts even when the engine is shut down and
the ignition switch is "off."
2. Without continuous power memory, all diagnostic and throttle sensor information is
lost. But all necessary information for system operation is regenerated automatically by
the ECU.
I. The ECU is a sealed component and is not serviceable in the field.
l. PROM removal and replacement is the only field service performed on ECU's.
Programmable Read Only Memory (PROM)
The Programmable Read Only Memory
(PROM) chip is the ECU's data bank.
A. It is programmable for a wide variety of
vehicle and equipment applications.
1 . It's the heart of the Electronic Control's
flexibility and programmability.
B. The PROM is programmed for specific
applications, options and characteristics.
l. Installing the wrong PROM can alter the
Electronic Control's performance.
c. The PROM is located inside the ECU and
is accessed through a cover in the ECU
case.
To determine which options are programmed on a specific PROM, access the
Electronic Control Inquiry System (ECIS).
A. ECIS is a computer program that offers on-line access to ECU and PROM
information.
Outtput Speed Sensor
The
e output speed sensor provid
des the Ellectronic Control
C
with output speed
info
ormation.
A. This
T
replaces the co
onvention
nal hydrau
ulic govern
nor system
m.
B. Speed
S
sen
nsor is loc
cated at th
he rear off the transsmission.
The
e output speed sensor has a magneticc pick-up that
t
"read
ds" the mo
ovement of
o the
spe
eed senso
or gear on the transsmission output
o
sha
aft.
A. Output
O
shaft rotatio
on causes the speed sensor gear's tee
eth to passs through
ha
mag
gnetic field at the end
e of the sensor.
B. As
A each to
ooth pass
ses, it crea
ates an electrical pu
ulse which is directted to the ECU.
1. The
T ECU uses
u
this signal to help control upshiftts, downsshifts and lock-up clutch
app
plication.
C. The
T on-hig
ghway sp
peed sensor uses a 16 tooth gear.
D. The
T off-hig
ghway sp
peed sensor uses 39
3 or 4l too
oth gears.
l. 50
000 and 6000
6
serie
es - 39 tee
eth.
2. 8000
8
and 9000 series - 41 te
eeth.
E. Off-highway speed sensors must be adjusted.
1. Align the sensor so it touches one of the trigger wheel's teeth if threaded all the way
in.
2.Thread the sensor in until it contacts the trigger wheel tooth, then back it out 3/4 to I
turn - be sure you're contacting the tip of the tooth (not between teeth).
Throttle Position Sensor
The throttle position sensor consists of a pull actuation cable and a linear
potentiometer.
A. One end of the cable is attached to the engine fuel lever shaft, the other end is
attached to the potentiometer inside the sensor's protective housing.
B. The sensor's housing has a plug for the wiring harness connector.
1. If the vehicle is equipped with DDEC II, an interface module may be required.
a. Two types of DDEC II interface modules are available - minimum interface and
maximum interface.
c. Throttle movement causes a change in the electronic signal to the ECU the ECU is
programmed to recognize the signal as "percent of throttle."
1. When the throttle is wide open, the ECU directs upshifts to occur near the engine
governed speed.
2. Part throttle causes upshifts to occur at lower engine speeds.
3. The difference between full throttle and part throttle upshifts is determined by the
shift calibration in the PROM.
The throttle position sensor indicates throttle position to the ECU.
A. The throttle position sensor replaces conventional hydraulic modulator pressure
valves and circuits.
B. The throttle position sensor is located in the engine compartment.
THROTTL
T
LE
P
POSITION
N
S
SENSOR
R
Throttle Position
T
P
S
Sensor
Operation
T senso
The
or's linearr
p
potentiom
meter
c
converts
t
throttle
m
movemen
nt into a
v
voltage
signal to
t ECU.
the
A As the wiper
A.
movves acrosss the resistive strip
p, resistan
nce chang
ges, varyin
ng the voltage the ECU
E
"cou
unts."
e throttle position
p
se
ensor produces anywhere frrom 0 to 255
2 countss for the ECU.
E
The
A. Its actual movemen
m
nt is only a small arrea within those 255
5 counts – 3/4 of an inch.
B. The
T senso
or should be adjustted to stayy within th
he service
eable area
a, out of th
he "error
zon
nes."
C. There is no optimum wide open or closed throttle count.
l. As long as the counts stay in a safe zone, the sensor works fine.
D. The "target zone" is 50 to 200 counts.
Throttle Position Sensor Self-Adjustment
The throttle position sensor self-adjusts to stay within the normal count area.
A. Every time the vehicle is started and the ECU is initialized the sensor is recalibrated.
l. The ECU stores the sensor's readings at vehicle shut-down.
2. when the ECU is powered, idle counts are increased by 15 from the previous
reading.
3. When the ECU is powered, the wide open throttle counts are decreased by 15 from
the previous reading.
a. This narrowed count is widened once the operator steps on the throttle - the ECU
reads actual sensor travel and continually re-adjusts to the highest and lowest counts.
4. The portion of the sensor's travel that is read by the ECU is small compared to the
actual available counts.
5. The sensor generally stays within the error zones and usually does not require
adjustment other than initial installation.
Throttle Position Sensor initial adjustment Initial throttle position sensor adjustment
should "Centre" the sensor between the error zones.
Throttle Position Sensor Mounting
Proper sensor function and cable longevity require proper cable alignment.
A. Do not exceed a 10 degree maximum installed cable angle.
l. Avoid excessive cable bends and linkage angles.
a. Do not exceed a 6-8 inch bend radius.
B. Linkages should move freely without binding or sticking.
1. Be sure the sensor's cable mounting won't interfere with throttle movement.
Mount the sensor securely on the chassis near the engine fuel control.
A. Avoid mounting to cantilever brackets or thin metal members.
B. Add protective shrouding if the sensor is mounted in an area susceptible to operator
or technician damage.
C. Mount the sensor on a flat surface (within .030") to avoid housing distortion.
D. The sensor itself should be mounted above the engine fuel control connection.
E. Shield the sensor and any of its components that are within 12 inches of
turbochargers, exhaust manifolds or other heat sources.
1. The sensor is designed to withstand250 degree continuous temperatures and 300
degree intermittent heat soaks.
Break-over levers are found on both on-highway and off-highway applications.
A. The throttle position sensor must read actual fuel shaft movement, not throttle
break-over movement.
B. If the sensor reads break-over movement, it will read the additional movement as
fuel shaft movement and self-adjust incorrectly.
Shift Selectors
The Electronic Control uses two general types of shifters - push button and lever.
A. V-731 applications use a three speed touch pad selector.
B. MT and some HT transmissions use the four and five speed push button selectors.
1. The HT also uses the four and five speed lever selectors.
C. Off-highway transmissions use lever selectors.
Drive by wire when the vehicle is equipped with an electronically controlled DDEC
engine the engine TPS will provide the throttle position to the transmission ECU
Pussh Button Shift Sele
ectors
The
e push buttton shift selector
s
h the "D
has
Do Not Shift" light lo
ocated on the shift pad.
A. The
T light cycles
c
on and off ass soon ass the syste
em is activvated (bulb check) and
during "hard"" failure.
1. The
T selecttor also ha
as a buzzzer that ma
ay sound during syystem mallfunction.
B. The
T selecttor should
d be moun
nted at no
o less than
n a 20 deg
gree angle from the
e
horizontal pla
ane.
Pussh Button Selector Bulb Replacement
The
e push buttton shift selector
s
h replacceable bullbs.
has
A. There
T
are two types
s of push button se
electors:
1. The
T old styyle had a membran
ne switch that was prone to cracking.
c
2. The
T new style
s
has a snap do
ome switch
h for extended servvice life.
a. Shift
S
selecctor covers
s are interchangea
able.
B. To
T replace
e bulbs:
1. Turn
T
the power
p
"off"" to the EC
CU and selector.
2. Remove
R
th
he shift se
elector mo
ounting sccrews and
d disconne
ect the ele
ectrical co
onnector
at th
he base of
o the sele
ector.
3. Remove
R
th
he screws
s retaining
g the cove
er and disconnect the multi-p
pin connecctor.
4. Replace
R
th
he bulbs.
a. With
W early style sele
ectors, the
e entire la
amp and socket
s
asssembly is replaced..
b. In
n new styyle selecto
ors, only th
he bulb iss replaced
d.
Levver Shift Selectors
S
Levver selecto
ors have eight
e
positions - R,N,D,5,4,3
3,2,1.
A. Shift patterns and detent (holding/releasing) mechanisms vary between
applications.
Lever selectors operate using Hall Effect magnetic switches.
A. The switches themselves are not serviceable, but Allison supplies a kit for the
selector's mechanical components.
Additional Sensing Components
Additional components that may provide input to the ECU include the temperature
sensor, pressure switches, and vehicle interface.
Temperature Sensor
The temperature sensor monitors sump oil temperature for the ECU.
A. Sensor is located in the valve body wiring harness.
l. On-highway is mounted on the solenoid control circuit.
2. Off-highway is mounted in the lock-up valve body.
When the oil temperature is too hot or cold, shifting is affected.
A. All shifts are blocked when the transmission is below -25 degrees (F).
B. Transmission has limited shifting (neutral, 1st, reverse) when it's -25 to +25 degrees
F.
C. Transmission operation is normal when 25 to 27O degrees (F).
D. Above 27O degrees (F), the hot light comes on (if equipped), a trouble code is
stored in memory, and top gear is inhibited.
1. Top 2 gears inhibited for off-highway transmissions.
2. Exception to the inhibit rule is special applications (emergency vehicles).
Pre
essure Sw
witches
The
e on-highw
way Electronic Con
ntrol uses three pressure swiitches to communic
c
cate
sign
nals to the
e ECU-rev
verse, forw
ward, and
d oil presssure switches.
A. These
T
are
e located on
o the ele
ectro-hydrraulic valvve body.
B. Reverse
R
a forward pressure switche
and
es signal the ECU when
w
the transmisssion is in
reve
erse or forward.
1. They
T
can be
b either of two styyles and plumb
p
dire
ectly into clutch
c
app
ply circuitss.
C. Oil
O pressu
ure switches signal the ECU when a lo
ow lube pressure or
o low oil le
evel
con
ndition exists.
T
are three diffe
erent type
es of oil pressure sw
witches:
1. There
a. Lube
L
pressure switc
ch.
b. Low
L
oil levvel pressu
ure sensorr.
c. Fluidic
F
oil level
l
sens
sor.
2. The
T transm
mission will
w only be
e equipped
d with one
e of these
e switchess.
a. The
T transm
mission as
ssembly number
n
de
eterminess the original switch
h for the
tran
nsmission.
b. The
T parts manual id
dentifies th
he latest switch
s
ava
ailable forr service.
c. The
T PROM
M and the chosen switch
s
must be com
mpatible.
1) The
T PROM
M must be
e program
mmed for the
t type of
o switch used.
u
Lub
be Pressure Switch
The
e lube pressure swiitch is con
nfigured like the forrward and reverse pressure
p
s
switches.
A. The
T lube pressure
p
switch
s
plu
umbs direcctly into th
he lubrica
ation oil pa
assage.
B. The
T lube pressure
p
switch
s
is a normallyy open sw
witch.
1. Lube
L
pressure close
es the sw
witch.
2. When
W
lube
e pressure
e is low, th
he switch opens, generating
g a trouble
e code.
Low
w Oil Leve
el/Pressurre Sensor
The
e low oil le
evel press
sure senso
or uses a separate housing that bolts to the bo
ottom with
the valve bod
dy.
A. An
A orifice in the sen
nsor's hou
using prod
duces a pressurized
d stream of oil thatt is
dire
ected to a switch on
n the oppo
osite side of the housing.
B. A bi-metall strip com
mpensatess for oil le
evel chang
ges as the
e transmisssion warm
ms up.
1. Itt blocks th
he flow of pressurizzed oil unttil the oil warms
w
up.
a. This
T
allowss the oil le
evel to rise before a trouble code is ge
enerated.
2. As
A the tran
nsmission
n warms, the
t bi-mettal strip moves
m
out of the wa
ay.
C. The
T low oil level pre
essure se
ensor is no
ormally op
pen.
l. If oil still rea
aches the
e switch affter transm
mission iss warm, th
he switch closes, ge
enerating
a co
ode.
D. Pressurize
P
ed oil can only reacch the switch if oil in the pan is too low
w.
1. Iff oil level is correct, it blocks the flow of
o pressurized oil.
Fluiidic Oil Le
evel Senso
or
The
e fluidic oil level sen
nsor is sim
milar to the low oil level pressure senssor, excep
pt it does
not use the bi-metal
b
sttrip.
A. The
T ECU is program
mmed to ignore
i
low
w level sig
gnals, untiil the temp
perature sensor
s
indicates the oil is warrm.
1. This
T
elimin
nates the need for the
t bi-metal strip.
B. The
T senso
or's housin
ng producces a presssurized stream
s
of oil.
C. The
T fluidicc oil level sensor is a normally closed switch.
1. When
W
presssurized oil
o contactts the pressure swiitch on the
e opposite
e side of the
t
hou
using, it op
pens the switch's
s
contacts, generating
g
g a trouble
e code.
D. Pressurize
P
ed oil can only reacch the switch if oil in the pan is too low
w.
1. Iff oil level is correct, it blocks the flow of
o pressurized oil.
Harrnesses
Elecctrical wirring harne
esses are used to connect
c
th
he compon
nents of th
he Electro
onic
Con
ntrol syste
em.
Chassis Wiring Harness
The chassis harness connects the throttle position sensor, output speed sensor and
electro-hydraulic valve body to the ECU.
A. Special connectors allow the harness to plug into the respective components,
including the bulkhead connector at the transmission, itself.
B. The wire numbers within the chassis harness are all 100 series numbers.
C. The chassis harness (and all harnesses) should be routed to avoid pinch points and
heat generating areas.
Cab Wiring Harness
The cab harness connects the shift selector and interface items to the ECU.
A. The interface connector comes three ways from Allison:
1. Two different types of connectors.
2. Loose wires.
B. The wire numbers in the cab harness are all200 series numbers.
C. This harness includes Bi-Directional Communication Link (BDCL) wires.
1. BDCL is used for vehicles equipped with DDEC I.
a. This allows the Electronic Control and DDEC to communicate.
2. DDEC II uses an interface module instead of BDCL.
The diagnostic data link (DDL) connector is part of the cab harness.
A. This connector is used to help troubleshoot the Electronic Control.
1. Service personnel can plug a display data line reader into the connector to monitor
trouble codes and system operation.
B. This connector should be located in a protected area on the vehicle.
Secondary Wiring Harness
The Sealed Plus II ECU is equipped to handle several additional options.
A. The secondary wiring harness connects these optional components to the ECU.
B. The secondary wiring harness comes from Allison with an ECU connector on one
end and loose wires on the other.
C. Some options wired through the secondary harness include:
1. Fire truck special logic.
2. Manual / automatic controls.
3. Range hold features.
4. Lock-up on and off.
5. Dual shift selectors.
6. Dual shift calibrations.
7. Bed hoist interlock.
8. Secondary spare input.
9. Additional special function input options.
D. Secondary harness wire numbers are 300 series numbers.
Identifying Electronically Controlled Transmissions
On--Highway Electronically Controlled Tra
ansmissio
ons - identifying fea
atures :
connecto
A. Bulkhead
B
or
B. Speed
S
sen
nsor
Off--Highway Electronically Controlled Tra
ansmissio
ons - identifying fea
atures:
A. Conventio
C
onal off-hig
ghway valve bodiess have few
wer pins in the maiin valve body
con
nnector.
B. Electronic
E
cally contro
olled transsmissionss have twiice as ma
any pins in
n the main
n valve
bod
dy connecctor.
1. Electronica
E
ally contro
olled transsmissionss also havve a smaller, soleno
oid-contro
olled lockup valve
v
bod
dy.
Elecctro-Hydraulic Valv
ve Bodies
The
e electro-h
hydraulic valve
v
bod
dy's functio
on is to su
upply oil pressure
p
a flow for
and
f
lubrrication, cooling
c
and clutch application
a
n.
A. An
A electro
onically co
ontrolled trransmission's hydrraulic circu
uits and valves are
con
ntrolled byy a series of solenoids.
B. These
T
solenoids arre activate
ed and deactivated by electriical signals generated by
the ECU.
C. The
T valve body also
o containss sensing switchess.
1. The
T forward pressure switch.
2. Reverse
R
p
pressure
switch.
s
3. Lube
L
pressure switc
ch.
Sole
enoids
Sole
enoids in the electrro-hydraulic valve body
b
act as
a switche
es to direcct hydraulic
presssure into
o specific passagess or to exh
haust.
A. Each
E
solenoid is po
ositioned on
o the vallve body so
s that so
olenoid pre
essure flo
ows to its
inle
et Port.
B. The
T inlet port
p is reg
gulated byy check ba
all position
n.
1. When
W
the solenoid is "off," th
he check ball
b is held
d down byy a plunge
er.
a. This
T
blockks the sole
enoid presssure portt, and exh
hausts solenoid pre
essure located
abo
ove the ba
all.
2. When
W
the solenoid is "on," th
he plungerr moves up,
u allowin
ng the che
eck ball to
o move.
a. This
T
blockks the exhaust port and allow
ws solenoiid pressurre to passs through.
C. Solenoids
S
s are eithe
er bolted or
o clamped to the valve
v
bodyy.
1. Clamped
C
s
solenoids
are "sand
dwiched" between the valve body and
d a mountting plate.
2. Bolted
B
sole
enoids are
e secured
d to the va
alve body with tom--head scre
ews.
D. The
T Electrronic Con
ntrol uses two gene
eral types of solenoids – latch
hing and nonn
latcching.
Latcching Sole
enoids
Latcching sole
enoids req
quire onlyy a short application
a
n of power to positio
on the solenoid.
A. When
W
latcching solenoids are momenta
arily energ
gized, the
ey move one
o direction and
stayy there un
ntil they arre energizzed again.
B. Clamp
C
dow
wn latchin
ng solenoids are ide
entified byy a single
e tab at the
e solenoid
d's base.
C. Bolt
B down
n latching solenoidss have a ta
ab Centre
ed betwee
en the two
o bolt hole
es.
Non
n-Latching
g Solenoid
ds
Non
n-latching solenoids
s require constant power to remain in position.
A. When
W
pow
wer is app
plied,-the non-latchi
n
ing soleno
oid movess into position and only
o
stayys there as
a long as
s it remain
ns energizzed.
B. Clamp
C
dow
wn non-la
atching so
olenoids have two ta
abs on the
eir base.
C. Bolt
B down
n non-latch
hing solen
noids have
e a tab sliightly off-C
Centre be
etween the
e two boltt
hole
es.
Typical On Highway Electro-Hydraulic Valve Body Operation
The Electronic Control's components and sensors eliminate the need for conventional
hydraulic governor pressure, modulator pressure and selector valves.
A. The output speed sensor provides the ECU with output speed information.
B. The throttle position sensor provides the ECU with throttle position information.
C. Electronic shift selectors provide operator input.
Based on these sensors, plus vehicle interface and oil pressure, temperature and level
input, the ECU energizes and de-energizes solenoids in the electro-hydraulic valve
body.
Hydraulic Components
A. Latching solenoids replace conventional shift signal valves.
1. They control the position of shift valves.
B. Shift valves control the flow of pressure into clutch apply circuits.
1. They can direct pressure into clutch apply circuits and they can exhaust clutch apply
circuits.
C. The neutral-range valve is controlled by one latching and one non-latching solenoid.
1. This valve controls the transmission's shifts from neutral to range, and from range
back to neutral.
D. The forward-reverse valve is controlled by a latching solenoid.
1. This valve controls whether the transmission shifts into a forward range or reverse.
E. Trimmer valves regulate oncoming clutch application.
F. The trimmer regulator valve is controlled by a non-latching solenoid.
1. The trimmer regulator valve controls the pressure under the trimmer valve plug,
which regulates trimmer valve operation.
G. The lock-up relay valve is controlled by a non-latching solenoid.
1. Depending on solenoid position, this valve exhausts or applies the lock-up clutch
apply circuit.
H. The solenoid priority valve and direction priority valve ensure steady flow of main
pressure regardless of transmission range or activity.
Solenoid Designations
Each solenoid has a letter designation and receives a constant flow of main pressure.
A. In four speed transmissions, solenoids B, C and D are latching and take the place of
conventional shift signal valves.
1. Solenoid B controls the 1-2 shift valve.
2. Solenoid C controls the2-3 shift valve.
3. Solenoid D controls the3-4 shift valve.
B. In five speed transmissions, solenoids A, B C and D are used.
1. Solenoid A controls the low-l shift valve.
2. Solenoid B controls the 1-2 shift valve.
3. Solenoid C controls the 2-3 shift valve.
4. Solenoid D controls the 3-4 shift valve.
C. In three speed models, solenoids C and D are used.
1. Solenoid C controls the l-2 shift valve.
2. Solenoid D controls the2-3 shift valve.
D. Solenoid F is latching and provides main pressure feed to the bottom of the forwardreverse valve.
E. Solenoid H is non-latching and directs main pressure to the bottom of the neutralrange valve when energized.
F. Solenoid J is latching and directs main pressure to the top of the neutral-range
valve.
G. Solenoid G is non-latching and directs main pressure to the lock-up relay valve
when the ECU senses the transmission is ready for lock-up.
H. Solenoid
S
E is non-la
atching an
nd provide
es a feed to the trim
mmer regulator valvve to help
p
con
ntrol shift quality.
q
The
e transmisssion shiftts when th
he ECU energizes and
a de-en
nergizes specific
s
so
olenoids.
Neu
utral Fluid
d Flow
When the en
ngine startts, main pressure
p
fiills all sole
enoid circuits.
A. It's then directed through the
e solenoid priority valve and cascadess through the
t 2-3
shifft valve, th
he l-2 shiftt valve an
nd into the
e 1st clutcch apply circuit.
B. Solenoid
S
J simply directs
d
ma
ain pressu
ure to the top
t of the
e neutral-range valvve.
1. This
T
keepss the valve position
ned down and prevents main
n pressure
e from enttering the
forw
ward clutcch apply circuit.
C. Since
S
onlyy first clutc
ch is appllied, the trransmission is in ne
eutral.
Firsst Range
When shifting
g into firstt range, solenoids F and H become
b
energized and solen
noid J is
de-e
energized
d.
A. Pressure
P
f
from
solenoid H po
ositions the neutral--range valve up, alllowing ma
ain
presssure to flow
f
to the
e forward-reverse valve.
v
B. Pressure
P
f
from
solenoid F positions the
e forward--reverse valve
v
up, allowing main
m
presssure to enter
e
the forward
f
cllutch apply circuit.
1. The
T forward clutch apply
a
circcuit also directs main pressure to the main
m
presssure
regulator, helping lowe
er main prressure once the fo
orward clu
utch is app
plied.
C. 1st
1 clutch remains applied
a
an
nd forwarrd clutch becomes
b
a
applied,
s
shifting
the
e
tran
nsmission into first range.
Seccond Rang
ge
Durring secon
nd range:
A. Solenoid
S
F stays op
pen becau
use it's lattching.
B. Solenoid
S
H (non-lattching) co
ontinues to
o receive positive voltage
v
an
nd also sta
ays open.
1. This
T
keepss forward clutch ap
pplied.
C. Solenoid
S
B become
es energizzed and directs pre
essure to the
t top of the 1-2 shift valve,,
forccing it dow
wn.
1. This
T
exhau
usts 1st clutch and directs main
m
presssure into the 2nd clu
utch applyy circuit.
D. Since
S
2nd
d clutch an
nd forward
d clutch are
a applied
d, the tran
nsmission attains se
econd
rang
ge.
Thirrd Range
Durring third range:
r
A. Solenoid
S
H remains
s energize
ed and so
olenoid F remains
r
la
atched op
pen.
1. This
T
keepss forward clutch ap
pplied.
B. Solenoid
S
B is latche
ed open and
a still feeds the 1-2 shift va
alve.
C. Solenoid
S
C is energ
gized and directs pressure to
o the top of
o the 2-3 shift valvve.
1. This
T
forcess the valv
ve down and allowss 2nd clutcch to exha
aust.
2. Main
M
presssure is no
ow directe
ed into the
e 3rd clutcch apply circuit.
D. Since
S
3rd and forwa
ard clutch
hes are ap
pplied, the
e transmisssion shiftts into thirrd range.
Fou
urth Range
Durring fourth
h range:
H and F keep forw
A. Solenoids
S
ward clutch applied.
B and C keep theiir shift valves down
B. Solenoids
S
n.
C. Solenoid
S
D is energ
gized and directs main
m
presssure to the
e bottom of
o the 3-4
4 shift
valvve, forcing
g the valve
e up.
1. This
T
exhau
usts 3rd clutch,
c
butt directs main
m
presssure into the
t 4th clutch apply circuit.
D. Since
S
4th and forwa
ard clutch
hes are ap
pplied, the
e transmisssion shiftts into fourth range.
Revverse
In re
everse, only soleno
oid H is en
nergized.
A. This
T
positiions the neutral-ran
n
nge valve "up."
1. In
n this possition, main pressurre flows th
hrough the
e forward-- reverse valve, thrrough the
3-4 shift valvve and into
o the 4th clutch
c
app
ply circuit..
B. Main
M
pressure from
m the solen
noid priority valve flows
f
throu
ugh the 2-3 shift va
alve, the
1-2 shift valvve and into
o the 1st clutch
c
app
ply circuit.
C. Since
S
1st and 4th clutches
c
are applied
d, the tran
nsmission attains re
everse.
The
e ECU dettermines how fast some
s
cluttches apply by energizing so
olenoid E.
A. This
T
directts main pressure to
o the trimm
mer regula
ator valve
e.
1. This
T
affectts trimmerr action byy controlling the pre
essure un
nder the trrimmer plu
ug.
Locck-Up
When the EC
CU determ
mines the appropria
ate conditiions have
e been me
et, solenoiid G
beccomes ene
ergized an
nd directss main pre
essure into
o the lockk-up clutch
h apply circuit.
Elecctrical Faiilure
The
e system'ss latching and non--latching solenoid
s
c
configurati
ion provid
des transm
mission
ope
eration during electrical failurre.
A. During
D
ele
ectrical failure, latch
hing solen
noids stayy in positio
on.
1. This
T
locks the trans
smission in
n range, inhibiting all
a shifts.
B. Non-latchi
N
ing soleno
oids become imme
ediately de
e-energize
ed, exhau
usting main
presssure.
1. Solenoid
S
G (if energ
gized) exh
hausts the
e lock-up clutch.
2. Solenoid
S
E no longe
er directs main presssure to the trimme
er regulato
or valve.
3. Solenoid
S
H stops th
he flow of main presssure to th
he bottom
m of the ne
eutral-rang
ge valve.
a. Main
M
presssure flowing throug
gh the valvve keeps it up and continuess to directt main
presssure to the forwarrd clutch apply
a
circu
uit.
b. As
A long ass the engine continu
ues running, the ne
eutral-rang
ge valve stays
s
up.
c. Once
O
the engine
e
is shut down
n and main pressure flow through the
e valve sto
ops, the
valvve moves down, ex
xhausting the forwa
ard clutch apply circcuit.
d. On
O re-starrt, if electrrical failure
e still exissts, the lattching sole
enoids co
ontinue to direct
presssure, butt the forward clutch
h is no lon
nger applie
ed, resulting in neu
utral.
Basic electronic control
Controlling Circuits
Switches provide a method to start and stop the current flow and control the circuit's
operation.
A. When "off," current flow cannot continue to the other side of the battery - the circuit
has an "open" portion between the positive and negative battery terminals.
B. When "on," a "closed" circuit is created - current can flow completely through the
circuit from the positive side of the battery, through the switch's conductor, through the
other components in the circuit, and back to the negative side of the battery.
Switches operate like valves in a hydraulic system.
A. If the valve is "on," it directs fluid through the rest of the circuit.
B. If the valve is turned "off," it stops the flow of fluid through the system or directs it
somewhere else.
When an electrical switch creates an open in the circuit, the current flow stops at the
switch.
A. When the circuit is properly designed, the voltage pressure cannot overcome the
open and the pressure stops there.
When an electrical switch is closed and completes the circuit, current flows through the
entire circuit and provides energy for the circuit's components to use.
There are different types of switches.
A. Manually operated switches require an operator to physically open or close a circuit.
B. Switches controlled by mechanical devices can open or close the circuit.
1. For instance, a mechanical switch can be placed in a hydraulic passage, and when
hydraulic pressure is present, the switch can open or close the circuit - this is a hydromechanical switch.
C. Switches controlled by other electrical circuits (electro-mechanical switches) are
called relays.
D. Electronic switches without mechanical function (such as Hall Effect switches) are
also utilized.
Electro-mechanical switches (relays and solenoids) operate using electromagnets.
Con
ntrolling Circuits
C
- Electroma
E
gnetism
Elecctromagnetism is created
c
wh
hen current flows th
hrough a coiled con
nductor.
A. Coiling
C
a wire
w and applying
a
v
voltage
to it createss a magne
etic field.
B. If a conductor (like a solid iro
on core) iss added to
o the midd
dle of the winding, the
t
mag
gnetic field is intens
sified.
Relays
e batteriess and swittches, rela
ays can be
b placed within an electricall circuit.
Like
A. Relays
R
op
pen and close circuits based on electriical input - they utilize
elecctromagne
etism to operate.
o
B. Relays
R
are
e common
nly used to
t allow lo
ow currentt circuits to
t control high curre
ent
circcuits.
1. Low
L
curren
nt circuits
s provide input to th
he relay which
w
open
ns or close
es the hig
gh currentt
circcuit.
C. Relays
R
ca
an be designed as "normally
"
open," orr "normallyy closed.""
1. Relay
R
term
minology is
s based on
o the "de
e-energize
ed" positio
on.
a. Iff a relay iss normally
y open, it's normallyy open in the de-en
nergized position
p
(n
no currentt
is flowing through the electro-m
magnetic portion
p
of the
t relay).
1) Normally
N
o
open
relay
ys are ope
en until th
hey are en
nergized - when the
ey're enerrgized,
theyy create a closed circuit.
c
2) Normally
N
c
closed
relays are closed until they are
e energize
ed - when energized, they
crea
ate an open circuit..
Sole
enoids
Ano
other type
e of compo
onent foun
nd in elecctrical circuits are so
olenoids.
A. In the Elecctronic Co
ontrol, solenoids arre the poin
nt where hydraulics
h
s interface
e with
elecctronics.
1. Hydraulic
H
f
flow
is dirrected by valves - the Electro
onic Control's solen
noids conttrol the
possition of th
he appropriate valve
es that dirrect fluid flow
f
through the va
alve body.
operate using
B. Solenoids
S
u
the same ele
ectro-magnetic princciples as relays.
1. A winding around a steel core produce
es a magn
netic field.
2. This
T
magn
netic field actually moves
m
a componen
c
nt inside th
he soleno
oid - the po
osition of
the compone
ent directs
s pressure
e to the ap
ppropriate
e locationss.
C. The
T Electrronic Con
ntrol uses two gene
eral types of solenoids – latch
hing and nonn
latcching.
1. When
W
latching solen
noids rece
eive powe
er they mo
ove one direction
d
a stay th
and
here until
theyy receive another signal.
s
a. They
T
latch
h into plac
ce when th
hey receivve a powe
er signal and
a remain in positiion
with
hout continuous power.
ng soleno
2. Non-latchi
N
oids require constant power to remain
n in positio
on.
a. When
W
pow
wer is applied, the solenoid
s
m
moves
into
o position.
b. When
W
pow
wer is turned off, the
e solenoid
d moves back
b
to itss original position.
p
D. Regardles
R
ss of theirr designation, latchiing and no
on-latchin
ng solenoiids act as electrohyd
draulic valvves.
1. They
T
direcct hydraulic pressurre using th
he theory of electro
o-magnetiism.
Circcuit Checkks
To check
c
voltage, the circuit sho
ould be energized.
A. Place
P
a te
ester lead on each side
s
of the
e electrica
al circuit or
o compon
nent.
B. The
T positivve lead frrom the te
ester is pla
aced on th
he positive
e side of the
t compo
onent or
circcuit and th
he negativ
ve lead is placed on
n the nega
ative side of the com
mponent or circuit.
C. When
W
trou
ubleshooting the Ellectronic Control,
C
voltage che
ecks are used
u
for
mea
asuring vo
oltage at various
v
lo
ocations, including ECU
E
main
n power in
nput and OEM
O
wiring and acccessories
s.
Ressistance becomes
b
an
a important troubleshooting
g measure
ement, an
nd it also is an
imp
portant facctor for ele
ectronic co
ontrol ope
eration.
A. One
O way the
t Electrronic Conttrol's Elecctronic Control Unit (ECU) monitors cirrcuit
stattus is by reading
r
circuit resisstance.
1. When
W
the Electronic
c Control is not perrforming properly,
p
y can ch
you
heck circu
uit or
com
mponent resistance
e to see if it is within
n design specificati
s
ons.
B. To
T check resistance
e, use an ohmmete
er.
1. A quality digital
d
volt//ohmmete
er allows you
y to che
eck resisttance and
d other keyy circuit
con
ndition item
ms.
2. Always
A
de
e-energize
e the circu
uit before performin
ng resistan
nce checkks.
Con
ntinuity ch
hecks are similar to
o resistancce checkss, but speccific resisttance readings are
not as critical.
A. Continuity
C
y indicates
s the presence of a complete
e, closed circuit
c
– th
he resista
ance of
thiss circuit (to
o a point) is not imp
portant.
l. Fo
or instancce, if a circ
cuit contains a swittch and tw
wo relays, and the switch
s
and
d relays
are closed, th
he circuit is comple
ete – continuity exissts.
B. Continuity
C
y and resis
stance checks are performed
d on de-e
energized circuits with
w an
ohm
mmeter.
1. Place
P
the leads on either
e
side
e of the circuit or co
omponent being ch
hecked.
2. The
T ohmm
meter sens
ses circuitt condition
n/resistan
nce - it sen
nds a sign
nal from one
o side
of th
he ohmme
eter, throu
ugh the ciircuit, bacck to the other
o
side of the ohmmeter.
C. Continuity
C
y and resis
stance ch
hecks are similar, but resistance is nott measure
ed by the
con
ntinuity check - this would req
quire a resistance check.
c
D. Most
M
digital volt/ohm
mmeters let you ch
heck resistance and
d continuitty.
E. Relationsh
R
hip between continuity and resistance
r
e:
l. If continuityy is present, the ressistance will
w be lesss than infiinite, and the circuit is
clossed.
2. Iff continuitty is not present, re
esistance will
w be inffinite - the
e circuit is open.
Che
ecking forr shorts is another electrical
e
c
check
- it's just as important
i
as voltag
ge,
resiistance an
nd continu
uity checkks.
A. Current,
C
like fluid in
n a hydrau
ulic system
m, takes th
he path of least ressistance.
1. Iff a hydrau
ulic hose breaks,
b
th
he pressurrized fluid
d comes out
o the bre
eak in the hose and
d
inhibits opera
ation of hy
ydraulic components in the circuit.
c
2. For
F electricity, if the
e conducto
or's insula
ator breakks and the
e conducto
or comes in contact
with
h another conducto
or, the elecctricity willl take the
e path of le
east resistance and
d
som
metimes in
nhibit the supply of energy to
o components in the circuit.
B. When
W
the conducto
or is not in
nsulated against
a
an
n alternate
e path of current
c
flo
ow, the
circcuit is said
d to be "sh
horted."
l. Exxample - If a circuitt had two wires run
nning rightt against each
e
othe
er (like a wiring
w
harness) and
d both wire
es' insulation broke
e at the sa
ame spot, the cond
ductors wo
ould shortt
toge
ether.
2. This
T
cause
es the currrent to flo
ow from one wire diirectly to the
t other wire,
w
bypa
assing
the rest of the circuit - the resultt is a non--functionin
ng circuit..
3. The
T circuitt could en
nd up dam
maged if th
he conducctors aren't designe
ed to hand
dle the
exccessive cu
urrent flow
w that occu
urs due to
o the shorrt – the wires could burn, or hopefully,
h
a fu
use will blo
ow.
C. Once
O
a sh
hort has occurred,
o
y can use
you
u the the
eories we
e've alread
dy discusssed to
find
d out wherre the problem lies - resistan
nce and co
ontinuity checks
c
ca
an lead uss right to
the problem.
Troubleshootting – Intrroduction
The
e Electron
nic Control is well-designed, but does encounte
er occasional proble
ems.
The
e chance for
f Electro
onic Control proble
ems is incrreased byy the number of ste
eps the
veh
hicle takess before re
eaching th
he custom
mer.
A. From
F
the factory,
f
th
he Electro
onic Contrrol goes to
o the OEM
M for insta
allation.
B. From
F
the OEM,
O
the vehicle iss often se
ent to a bo
ody specia
alist.
C. Like
L
the OEM
O
and body
b
speccialist, the
e distributo
or may ne
eed to perrform som
me work
on the
t vehicle before it's
i finally forwarded
d to the cu
ustomer.
Eacch of these steps presents a potential problem area.
A. Installation
n, interfac
ce and tecchnician mistakes
m
o
often
causse system
m trouble.
B. The
T Electrronic Control will so
ometimess record diiagnostic informatio
on in the form
f
of
trou
uble codess.
l. Th
hese code
es lead te
echnicianss to potential proble
em areas.
Som
metimes, problems occur tha
at don't se
et trouble codes.
A. this requirres following the ste
eps to isolate mech
hanical, hyydraulic or
o electrica
al
problems
And
d sometim
mes, problems occu
ur that cau
use interm
mittent trou
uble code
es.
A. This
T
requires follow
wing the stteps for trroubleshooting code
e and non
n- code prroblems.
Insttallation Checklist
C
proper Ele
ectronic Control com
mponent installation
n can cau
use a varie
ety of perfformance
Imp
problems. Be
efore troubleshootin
ng, use th
he Electronic Contro
ol Installa
ation checklist to
enssure prope
er compon
nent insta
allation.
ECU
U is moun
nted in an area prottected fro
om exposu
ure to dusst, weathe
er, sunlight and
clea
aning spra
ays.
ECU
U is moun
nted securely and in an area
a that remains cool and supp
plies good air flow.
ECU
U and con
nnectors are
a proteccted from road spla
ash or othe
er sources of moistture.
ECU
U power leads are kept as short as po
ossible, aren't route
ed next to
o voltage or
o
amp
perage sp
pike generators and
d are dedicated for the ECU only.
to chassiss near the
Wirre 201 is securely
s
grounded
g
e ECU.
Push button shift selector is mounted in an area protected from moisture and high
concentrations of sunlight.
Push button shift selector is mounted at least 20 degrees from horizontal to allow
moisture to drain.
Selector is mounted where it will not be immersed in water.
"Check transmission" light is mounted so that it is clearly visible in all conditions
(sunlight, night, etc.).
Throttle position sensor cable and linkage is routed so that no binding occurs during
accelerator/sensor operation.
Throttle position sensor cable end does not exceed a 10 degree maximum installed
angle.
Throttle position sensor is reading actual throttle shaft movement, not break over lever
movement.
Throttle position sensor is mounted flat (within .030") on a solid chassis member near
the engine fuel control.
Throttle position sensor is protected from excessive heat, moisture and potential
operator/technician damage.
Throttle position sensor is mounted so that moisture can drain from the sensor's body
(body should be mounted above the cable).
The DDL connector is mounted in a protected area, preferably in the cab.
Wiring harnesses are securely mounted to prevent rubbing, bending, chafing and other
harmful movement.
The speed sensor pickup is not connected to any devices except the Electronic Control
wiring harness.
Trouble Code
es
e Electron
nic Control's self-dia
agnosis ca
apabilitiess help you
u locate and repair
The
problems.
A. The
T Electrronic Control's ECU
U is a miccro-processsor with prep
progrrammed operating
o
limits.
1. Iff the ECU
U receives
s signals th
hat are no
ot within programm
p
med limits, it turns on the
"Ch
heck Transsmission"" light and a diagno
ostic troub
ble code iss stored in
n memoryy.
Trouble code
es fall into
o one of tw
wo catego
ories - softt or hard.
A. Soft
S codess:
1. Cause
C
the
e "Check Transmiss
T
sion" light to come on.
2. Do
D not cau
use the EC
CU to inhibit transm
mission op
peration.
B. Hard
H
code
es:
1. Cause
C
the
e "Check Transmiss
T
sion" and "Do Not Shift"
S
lightts to come
e on.
2. Limit
L
the operation
o
of
o the tran
nsmission
n, protectin
ng it from damage.
Rettrieving Trrouble Co
odes Witho
out Pro-Liink
To retrieve trrouble cod
des withou
ut using diagnostic
d
c equipme
ent:
A. Turn
T
the ig
gnition "on
n" and sta
art the eng
gine.
B. Run
R the engine at id
dle with th
he shift se
elector in neutral.
C. Place
P
and
d hold the Electronic Control''s test swiitch in the
e "on" position.
D. The
T "Checck Transm
mission" light will fla
ash the most imporrtant diagn
nostic cod
de if one
is present.
p
1. For
F examp
ple - Flash
h-Pause-F
Flash-Flassh-Flash denotes
d
a Code 13
3.
2. There
T
mayy be a sec
cond code
e in memo
ory, but it will not fla
ash.
Diagnostic eq
quipment must be used to re
etrieve ad
dditional co
odes.
To clear
c
trouble codes
s without using
u
diag
gnostic eq
quipment:
A. Turn
T
the vehicle
v
"offf."
B. Place
P
the test switc
ch in the "o
on" positio
on.
C. Be
B sure th
he vehicle
e's brakes are applied.
D. Restart
R
the vehicle..
E. Select
S
revverse (stay
y in reversse for a co
ouple of seconds)
s
t
then
returrn to neutral.
Retrieving trouble codes using the Pro-link
To retrieve trouble codes using the Pro-link:
A. Connect the diagnostic tool to the Electronic Control's DDL.
B. Select the transmission type.
C. Press "Function" to enter the Function Selections Menu.
D. Scroll until "Diagnostic Codes" appears, then press "Enter."
To clear trouble codes using the Pro-link:
A. Leave the Pro-link Plugged into the DDL.
B. Cycle the ignition switch "off" then back "on."
C. Move the shift selector from neutral to reverse, then back to neutral.
Troubleshootting Scenario #1 - Troublesh
T
hooting Co
ode 12
Cod
de 12 indicates the ECU is re
eceiving a low lube
e pressure
e signal.
A. Possible
P
n
non-electr
rical cause
es include
e low oil le
evel or low
w oil presssure.
B. Possible
P
e
electrical
causes
c
include a fa
aulty presssure switcch, an ope
en or shorrt in the
cha
assis wirin
ng harness
s, or an open or short in the transmisssion intern
nal wiring harness.
Let''s assume
e the non--electrical causes have
h
been
n checked
d and are okay – the
tran
nsmission's Electronic Contro
ol system
m must be checked.
Elecctronicallyy Controlle
ed transm
missions are
a equipp
ped with one
o of thre
ee types of
o oil
presssure switches - lube pressu
ure switch
h, low oil le
evel presssure senssor or fluid
dic oil
leve
el sensor.
A. Lube
L
presssure switc
ch is open
n when no
o pressure
e is prese
ent and clo
osed whe
en
presssure exissts.
l. A trouble code sets when
w
the vehicle iss running and the circuit
c
stayys open.
B. Low
L
oil levvel pressu
ure sensor is open when no pressure is presen
nt, and, be
ecause of
its design,
d
re
emains op
pen when pressure exists.
1. A trouble code
c
is se
et when th
he vehicle
e runs and
d the circu
uit closes.
C. Fluidic
F
oil level sensor is norrmally clossed.
1. When
W
the vehicle ru
uns, the sw
witch stayys open, and
a a code is set when
w
the switch
s
closses.
Dettermine which
w
switc
ch the tran
nsmission
n uses (refer to ECIIS).
A. For
F our sccenario, as
ssume a lube
l
presssure switcch is used
d - the circcuit should
d be open
n
whe
en the veh
hicle is sto
opped and
d closed when
w
it's running.
r
B. The
T ECU has set a trouble code,
c
so it must be reading th
he circuit as open.
Isolate the prroblem - determine
d
e if it is insside the tra
ansmissio
on (interna
al wiring or
o switch)
or outside
o
the
e transmis
ssion (cha
assis wirin
ng harnesss).
A. Isolate the
e chassis wiring harness by unpluggin
ng it from the transm
mission, the speed
sen
nsor, throtttle sensorr and the ECU.
B. Check
C
the
e circuit inside the transmissiion and th
he chassiss harness for open and
sho
orts.
l. Pe
erform sim
mple circu
uit checks - continuity checkss.
2. Check
C
the circuit ins
side the trransmission with th
he vehicle
e running.
3. Check
C
for continuity
y between
n terminalss H and E on the trransmissio
ons bulkh
head
con
nnector.
A. If continuitty exists, the circuitt is closed
d - the ope
en signal must be coming
c
fro
om
som
mewhere else.
e
B. If continuitty doesn'tt exist; the
e open sig
gnal is pro
obably com
ming from
m the interrnal
circcuit, eitherr the switc
ch or its re
elated wiriing harnesss or the wiring
w
circcuit board
d or faulty
or damaged
d
terminals.
Notte: The Allison Tran
nsmission
n Electronic Controll Troublesshooting Manuals
M
p
provide
spe
ecific information for testing the
t switch
h (using lig
ght air pre
essure) an
nd tracing an
inte
ernal wiring harness
s/wiring board prob
blem.
If th
he internal circuit is sending a closed signal,
s
the
e problem
m probablyy lies in the chassiss
wiring harnesss. wires 101 and 122
1 provid
de the EC
CU with the
e sensing
g signal, so check
thesse wires for
f opens and shortts.
A. It's difficult to place the volt/o
ohm meter connecttors on ea
ach end off the wirin
ng
harness, so you
y can in
nstall jump
per wires while the harness is isolated
d. (Examp
ple:
jum
mping term
minals H and E on th
he transm
mission en
nd of the chassis
c
ha
arness connects
wire
es 101 an
nd 122 tog
gether.)
B. Now
N
deterrmine if th
he chassiss harness circuit is open by checking
c
f continuity
for
betw
ween term
minals 2N and 3N on
o the EC
CU side of the chasssis harnesss.
1. Iff continuitty exists, the
t circuitt isn't open, but a short may be presen
nt.
2. Iff continuitty does no
ot exist, one or both
h of the wires
w
may be open
Asssume that we found
d an open in the chassis harn
ness circu
uit - when we checkked
term
minals 2N and 3N on
o the EC
CU side of the chasssis harnesss, we did
dn't have
con
ntinuity.
A. Isolate and check each
e
of the
e wires in the circuit, starting
g with wire
e 101.
l. Remove the jumper between terminalss H and E and place
e it between termin
nals E and
d
L.
2. Assuming
we don't have anyy other trouble code
A
es, wire 10
09 should
d be good - it
sho
ould have continuity
y from term
minal E to
o terminal 2Yon the
e other end of the harness.
h
3. Place
P
the jumper
j
be
etween terminals E and L - check
c
for continuity
c
y at termin
nals 2N
and
d 2Y at the
e ECU end of the chassis
c
ha
arness.
a. Iff continuitty exists, wire
w 101 is
i not ope
en.
b. Iff continuitty does no
ot exist, wire
w 101 iss open and
d must be
e repaired
d.
Notte: Make sure
s
the wire
w you're
e jumping to is good - make sure no other
o
code
es exist
thatt might afffect the wire
w you're
e using to test the trroubled ciircuit.
B. Use
U the sa
ame apprroach to issolate wire
e 122.
1. Jump
J
term
minal H to another chassis
c
ha
arness wirre (for thiss scenario
o, use wire
e 118 term
minal F on
n the trans
smission side
s
of the
e chassis harness)).
2. With
W terminals H an
nd F jumpe
ed, contin
nuity shou
uld be pressent at terminals 3N and 2P
on the
t ECU side
s
of the
e chassis harness.
a. Iff continuitty exists, wire
w 122 is
i not ope
en.
b. Iff continuitty does no
ot exist, wire
w 122 iss open and
d must be
e repaired
d.
Eve
en if wire 122
1 and 101
1 are no
ot open, th
hey mightt be shorte
ed to grou
und or sho
orted to
ano
other wire in the harness. Ch
heck for sh
horts to grround by isolating the
t appropriate
wire
e (disconn
nect the harness att both end
ds).
A. Place
P
one
e end of th
he tester on
o the app
plicable te
erminal an
nd the other end of the testerr
on a good grround.
l. If continuityy exists, th
he wire is shorted to
t ground and mustt be repaired.
Che
ecking wirres for sho
orts to oth
her harnesss wires requires
r
to
otal wire issolation.
A. Unplug
U
the
e harness
s at both ends
e
and remove all
a jumperss.
B. Place
P
one
e test lead on the ap
pplicable terminal and
a use th
he other le
ead to pro
obe all
othe
er termina
als.
1. No
N continu
uity should
d exist be
etween terrminals un
nless the wiring
w
dia
agram calls for two
wire
es to merg
ge somew
where in th
he harnesss.
2. Iff continuitty exists between
b
te
erminals, the appliccable wire
es are sho
orted to ea
ach other.
Thiss problem
m must be corrected
d for prope
er Electro
onic Contrrol operatiion.
Troubleshootting Scenario #2 -T
Troubleshooting Co
ode 21
de 21 indicates the ECU is re
eceiving an
a incorre
ect signal from the throttle
t
po
osition
Cod
sen
nsor or its related ciircuits.
A. Possible
P
n
non-electr
rical cause
es include
e faulty throttle/thro
ottle senso
or linkage,
imp
proper thro
ottle sensor installa
ation (on break-ove
b
er lever, ettc.), impro
oper throtttle sensorr
adju
ustment or
o a bindin
ng throttle sensor ca
able.
1. Physically
P
checking
g the throtttle positio
on sensor''s mountin
ng and me
echanical
ope
eration will identify or
o elimina
ate these potential
p
p
problem
a
areas.
B. Possible
P
e
electrical
causes
c
include a fa
aulty throtttle sensorr, an overr-stroked throttle
t
sen
nsor, or an
n open or short in th
he chassis harnesss.
Let''s assume
e the non--electrical causes have
h
been
n checked
d and are okay – the
tran
nsmission's Electronic Contro
ol system
m must be checked.
A. Sometime
S
es, the thro
ottle senssor's self-a
adjustmen
nt mode will
w read an "over-sttroke"
con
ndition eve
en though
h the senssor is operrating and
d installed properly..
1. Cycling
C
the
e ignition switch "on" and "offf' severall times willl allow the
e sensor to
t selfadju
ust and co
orrect the situation..
2. Iff the code
e still appe
ears after clearing it
i from the
e ECU, the
e problem
m still exists and
you
u must con
ntinue trou
ubleshootting.
Isolate the th
hrottle sen
nsor by dissconnecting the chassis wiring harnesss.
A. Verify
V
thro
ottle position sensor operatio
on by perfforming re
esistance measurem
ments.
If th
he sensor checks okay,
o
the chassis
c
ha
arness mu
ust be che
ecked for opens an
nd shorts.
A. Disconnec
D
ct the cha
assis harness from all compo
onents - in
ncluding th
he ECU,
tran
nsmission, speed sensor and
d throttle sensor.
s
B. Check
C
eacch wire in the throtttle sensorr circuit for shorts to
o ground.
1. Connect
C
o end off the teste
one
er to groun
nd and the
e other en
nd to the appropria
a
te
term
minal at th
he ECU en
nd of the chassis harness.
2. Iff continuitty exists anywhere,
a
, the wire is shorted
d to groun
nd and mu
ust be rep
paired.
C. Check
C
eacch wire in the throtttle sensorr circuit fo
or shorts to
o other wiires.
1. Connect
C
o end off the teste
one
er to the appropriate
a
e circuit te
erminal att the ECU
U end of
the chassis harness.
h
2. Check
C
for continuity
y by placin
ng the oth
her tester lead on each
e
termiinal at the
e ECU
end
d of the ha
arness.
3. Iff continuitty exists anywhere,
a
, the wire is shorted
d to anoth
her wire an
nd must be
b
repa
aired.