Chapter 20
Electronically
Automated Standard
Transmissions
Objectives (1 of 2)
• Explain how a standard mechanical transmission is
adapted for automated shifting in three-pedal and
two-pedal systems.
• Identify three different OEM automated
transmissions and interpret the serial number codes
of each.
• Describe the hardware changes that differentiate a
standard Roadranger twin-countershaft
transmission from its electronically automated
version.
• Outline the electronic circuit components that are
used to manage AutoShift transmissions.
Objectives (2 of 2)
• Outline the main box and auxiliary section actuator
components required for AutoShift electronically
automated, standard transmissions.
• Describe how the electronic circuit components
work together to perform the system functions.
• Perform some basic diagnostic troubleshooting on
automated transmission electronics.
• Describe the ZF Meritor SureShift and FreedomLine
transmissions and the Mercedes Benz AGS
transmissions.
Transmission Identification
• The best way of identifying transmission
specifications on a vehicle is by accessing
the chassis data bus, specifically the 130
MID for generic ESTs.
AutoShift (1 of 2)
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Serial Number: RTAO – 14710 B AS
R Roadranger
T
Twin countershaft
A Automated
O Overdrive
(X)100 + 50 = nominal torque capacity
7
Design level (5 = spur gear, 6 = multimesh gearing,
7 = multimesh front, helical auxiliary gearing)
• 10 Number of forward speeds
• B Ratio set designation (C)
• AS AutoShift
AutoShift (2 of 2)
UltraShift
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Serial number: RTO - 14 9 10 B - DM 2
R Roadranger
T Twin countershaft
O Overdrive
14 Torque capacity
9 Design level
10 Forward speeds
B Ratio category
DM UltraShift with DM clutch
2 Automation level/Gen II electronics
Freedomline
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Serial Number: M O – 16 Z 10 C - A 18
M ZF Meritor
O Overdrive (no letter = direct drive)
16 Input torque rating: 1,600 lb./ft.
Z Design platform: Z = FreedomLine F = 9 speed
G = 10 speed
10 Number of forward gears
C Ratio
A Automated (S = shift by wire, M = manual)
18 Highest torque in top 2 gears = 1800 lb./ft.
Mercedes Benz AGS
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Serial Number: MBT – 560 S - 6 O
MBT
Mercedes-Benz Transmission
560
Input torque rating 560 lb./ft.
6
Number of forward ratios
O
Overdrive (D 5 direct drive)
UltraShift Two-pedal
Automated Transmission
Mercedes-Benz AGS
Two-pedal Automated Transmission
AutoShift Components
• The Eaton Fuller Roadranger AutoShift automated
transmission is a two-module system.
– The System Manager (ECU) does the “thinking.”
– A second module, the transmission controller (ECU),
converts that thinking into action by performing the
switching functions of the transmission.
• AutoShift transmission components can be grouped
as follows:
– Base standard gearbox
– Transmission automation components
– Vehicle automation components
Base Transmission
• The AutoShift transmission is based on a Roadranger twincountershaft platform.
• A Fuller 10-speed transmission has a 5-speed main or front
case, with a 2-speed auxiliary section.
• Although the base transmission has a similar appearance to
non-automated versions, the following changes are required:
– Main box. Two screw bosses have been added to the case so
the transmission controller can be mounted to the side.
– Range cylinder cover. The range cylinder cover is altered to
house the range shift control mechanism.
– Shift bar housing. The shift bar housing has been machined to
accept the speed sensors.
– Shift yokes. The shift yokes have been hardened at the fork
pads to improve durability during shifts.
Automation Components
• The transmission automation components
include:
– X–Y shifter
– Speed sensors
– Power module
– Transmission harness
– Range valve
– Reverse switch
– Transmission controller
Electric Shifter Assemblies
• The shift shaft is a square
section shaft.
• The shift finger rides on the
shift shaft.
• This permits the shift finger to
be moved along the rail.
• The shift shaft has a machined
area on the end to enable it to
rotate the position sensor.
• The gear select yoke also
rides on the shift shaft. The
yoke is driven by the gear
select ball screw, which
rotates the shift shaft for gear
selection.
• The gear select sensor
provides position data to the
transmission controller.
Ball Screw Assemblies (1 of 2)
• The shift finger position is located by a pair of
ball screws.
• One ball screw is used for the lateral (left to
right) movement that is required to select the
correct rail.
• The other ball screw is used for the forward
or backward positioning required to select a
gear.
Ball Screw Assemblies (2 of 2)
• The ball screw assembly is
made up of a worm gear,
ball screw nut, and ball
bearings.
• When the worm gear
rotates, the ball bearings
ride in the grooves of the
worm threads.
• When a ball reaches the
end of a ball screw block, it
is forced into a tube to be
returned to the beginning of
the worm threads in the ball
screw block.
Rail Select Ball Screw
• The gear select ball screw nut has a pair of
tabs, one on either side.
• These tabs drive the gear select yoke, which
is located on the shift shaft with the shift
finger.
• When gear selection is commanded, the ball
screw block moves the gear select yoke,
which in turn moves the shift shaft.
Electric Motors
• The motors use a
permanent magnet
operating principle and are
capable of forward or
reverse rotation.
• The rail select motor is
pinned directly to the rail
select ball screw and the
gear select motor is pinned
directly to the gear select
ball screw.
• The electric motors used in
each ball screw assembly
are not interchangeable.
Position Sensors (1 of 2)
• Position sensors convert a
mechanical position to a
signaled voltage value that is
then returned to the ECU.
• AutoShift position sensors are
three-wire voltage dividers.
• They are supplied a reference
voltage of 5V, modulated by
the ECU.
• There is a resistor between
the 5V input terminal and the
ground connection.
• A wiper contacts the resistor
and, depending on its
mechanical location,
determines the signal voltage
value returned to the ECU.
Position Sensors (2 of 2)
• The rail select sensor is connected to the rail select
ball screw. The position sensor yoke arm fits over a
pin on the side of the rail select screw block. Its
signal allows the transmission controller to
determine whether the shift finger is located over
the correct rail before effecting a shift.
• The gear select sensor monitors shift finger position
during gear selection. The signal returned to the
transmission controller confirms whether a shift has
been successfully effected.
Shop Talk
• Current versions of AutoShift are designed to
break driveline torque when a predetermined
driveline (road) speed is sensed.
• This prevents driveline component stall
damage to the engine.
Range Valve Operation (1 of 2)
Range Valve Operation (2 of 2)
Speed Sensors (1 of 4)
• Three speed sensors are used
in the transmission. They
measure and report:
– Input shaft speed
– Mainshaft speed
– Output shaft speed
• When the teeth of the pulse
wheel cut through the
magnetic field in the sensor,
an AC voltage is induced in
pulses.
• The AC voltage value and
frequency produced will rise in
proportion to the increase in
rotational speed.
• These sensors can be tested
by measuring voltage output.
Speed Sensors (2 of 4)
• The input shaft speed sensor
is located at the right front
corner of the shift rail housing.
• The speed sensor magnet and
coil produce pulses from the
upper countershaft PTO gear.
• The AC voltage and frequency
rise proportionally with shaft
speed.
• The ECU measures the
frequency of the pulses, not
the actual voltage generated.
• Input shaft speed is calculated
by multiplying countershaft
speed by the head set ratio.
Speed Sensors (3 of 4)
• The mainshaft speed sensor is located at the
left rear corner of the shift rail housing at the
auxiliary countershaft drive gear.
• A pulse generator principle is used; the AC
voltage and frequency produced and sent to
the ECU increase proportionally with shaft
rotational speed.
• The auxiliary countershaft drive gear is
meshed to the mainshaft through the
auxiliary drive gear and is driven at the same
speed.
Speed Sensors (4 of 4)
• The output shaft speed sensor picks up pulses
produced by a tone ring located on the output shaft.
• This tailshaft-located sensor inputs road speed data
to the AutoShift transmission controller and to other
chassis electronic systems.
• Road speed is determined by factoring the output
shaft speed with the drive axle carrier ratio and the
rolling radius dimension of the tires.
• A standard 16-tooth pulse wheel is used.
Function of the Speed Sensors
• Shift synchronization
– Input shaft speed and mainshaft speed data is used by
the transmission controller for synchronizing shifts in
the transmission main box.
• Verifies range engagement
– The data generated by the mainshaft and output shaft
speed sensors is used by the transmission controller to
verify range engagement.
• Reports road speed data
– The output or tailshaft speed sensor data may also be
shared with other chassis electronic systems as vehicle
road speed data.
Power Module (1 of 2)
• The power module is located
on the transmission controller
next to the electric shifter unit.
It incorporates the following
components:
– Cycling circuit breakers
– Reverse voltage diode
– Reverse voltage Zener diode
• The power module connects
the vehicle electrical system
with the transmission electrical
and electronic systems and
protects the transmission
electrical system from current
overloads with cycling-type
circuit breakers.
Power Module (2 of 2)
• The AutoShift power module
contains two SAE #1 cycling
circuit breakers:
– One rated at 25 amps. The
25-amp breaker protects
the circuit supplying the
electric shifter motors and
the logic battery power
from current overloads.
– The other at 10 amps. The
10-amp breaker is located
in series in the circuit
supplying logic battery
power following the 25amp breaker.
Reverse Voltage Diode
• The reverse voltage diode is located just past the
25-amp circuit breaker. The diode permits current
flow in one direction only. In the event of a reverse
polarity condition, the reverse voltage diode blocks
current flow into the transmission electrical circuit.
Reverse Voltage Zener Diode
• The reverse voltage zener diode is located between the negative
terminal on the reverse voltage diode and battery ground.
• The zener diode functions as a normal diode but acts to regulate
voltage should it exceed a specified level.
• The reverse voltage zener diode used in the AutoShift power
module will permit current flow, although it will not permit the
voltage value to exceed 32V.
Power Module Functions
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Motor Power. Connected to the vehicle cranking motor, the circuit passes through
the 25-amp circuit breaker and the reverse voltage diode and connects to the
motor terminals.
Motor ground. The motor is direct grounded through the power module by means
of a wire to the cranking motor ground terminal.
Logic power. Logic power refers to the electric feed required to power up the
system ECUs. It is routed from the vehicle cranking motor battery terminal through
both the 25-amp and 10-amp circuit breakers.
Logic ground. The logic ground is routed direct from the cranking motor ground
terminal through the power module and out to the logic power connector.
Transmission Controller
• It has some limited processing
capability but is mainly
responsible for managing the
switching requirements of the
system.
• The transmission controller
ECU is multiplexed.
• It is connected to the system
electrical/electronic circuit by
means of a dedicated harness
known as the transmission
harness.
• All of the input and output
circuits are connected to the
transmission controller by
means of this harness,
including the data link to the
system manager.
Inertia Brake
• The inertia brake system on
an AutoShift transmission
helps stop the countershafts
on initial engagements when
the clutch is either out of
adjustment or defective.
• The inertia brake is mounted
at the 6- or 8-bolt PTO.
• The inertia brake consists of a
solenoid and brake.
• The solenoid controls the
inertia brake by switching
regulated air pressure to the
inertia brake piston to apply
the friction and reaction discs,
which brakes the countershaft.
Caution
• When removing the inertia brake solenoid,
ensure that system air pressure is completely
relieved and the air/filter regulator is
removed.
Vehicle Automation
Components
• The vehicle automation components connect the
transmission electrical and electronic circuits with
those of the vehicle. This group of components
includes:
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System manager
Gear display
Shift lever
Power connect relay
Start enable relay
Vehicle harnesses
System Manager
• The system manager ECU is a second
microprocessor module with the dual functions of
interfacing with the rest of the vehicle and overall
management of the transmission systems.
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Controlling logic power
Managing shifting
Processing fault conditions
Processing shift lever commands
Controlling Service and Wait lights
Providing information to lever digital display
Caution
• The shifter module must be calibrated before
a vehicle is placed in operation.
Data Retention
• The system manager stores fault code data
in its nonvolatile RAM before turning off the
power connect relay during each shutdown.
• Service light
– The service light displays
fault information to the
driver or technician.
– A flashing or continuous
illumination of the service
light indicates that a fault
code has been logged.
– Logged fault codes can
then be pulse displayed
by flashing numeric codes
on the service light.
• Wait light
– The wait light was only
used on the earliest
versions of
AutoSelect/AutoShift.
– On those transmissions
using a wait light, it is
illuminated on power-up
when the system manager
and transmission controller
perform a self-check
sequence.
– If the transmission checks
okay, the wait light turns off.
• Speaker
– The speaker tone is
used to alert the driver
to break torque on the
driveline so that a shift
can be effected.
– The tone signal is
output by the system
manager.
• Detents
– The detent mechanism
locates the
transmission shift lever
in the correct location
in each range select
position.
– It provides an element
of gearshift feel to the
driver when shifting
from one gear to
another.
Gear Display
• When a shift is initiated, the
target gear is displayed
continuously.
• When the transmission shifts
to neutral, the target gear
begins to flash.
• When the shift sequence is
completed, the display ceases
to flash and the range status is
displayed.
• Up arrows indicate the input
shaft speed must be increased
until it matches main shaft
speed.
• Down arrows indicate the
input shaft speed must be
decreased to match the main
shaft speed.
Vehicle Harnesses (1 of 2)
Vehicle Harnesses (2 of 2)
Tower Harness Service Port
• The service port is located in
the tower harness. It is used to
access circuits for voltage
checks. The circuits can be
checked without separating
harness connectors.
– Pin A: ignition power
– Pin B: dummy
– Pin C: measures voltage at
the power connect relay
– Pin D: ground
– Pin E: start enable relay coil
– Pin F: dummy
– Pin G: power connect relay
coil; output from the system
manager
Fallback Modes
• When a fault code is logged, the transmission
electronics are designed to assess all
remaining functionality and then default to a
limited operational mode.
– Five-speed fallback
– One-speed fallback
– In-place fallback
– Downshift fallback
Fault Code Status
• An active code indicates a problem active at the
time of reading the system.
• An inactive code (historic code) indicates the
occurrence of a fault that has either occurred in the
past or is not detected at the moment of reading the
system.
• The presence of an inactive code may indicate that
the vehicle has not been driven in the proper
manner.
• AutoShift system troubleshooting should be
performed using the AutoShift service literature that
contains step-by-step troubleshooting guides.
Pretests
• Transmission pretests should be performed
before progressing to specific fault code
isolation.
• Pre-checks require that electrical inputs and
pneumatic supply to the transmission be
functioning properly.
• The pretests eliminate obvious high-level
problems immediately before progressing to
a detailed, sequentially stepped diagnostic
procedure.
Symptom-driven Diagnostics
• No fault code
– A transmission is, above all, a mechanical
device, and problems will occur in which
active or inactive electronic codes are not
logged.
• Mechanical faults
– Never assume that every fault must be
electronically monitored.
CEEMAT
• This was an early, not too successful effort by
Eaton at an automated transmission system.
• The acronym stands for converter enhanced,
electronically managed, automated
transmission.
• You do see a few CEEMAT automated
transmissions around, but more likely in a
college or teaching environment rather than
on the highway.
Engine SynchroShift (ESS)
• Rockwell Meritor introduced Engine SynchroShift (ESS) in 1997
just before their merger with the German company ZF.
• ESS is a three-pedal system designed to synchronize engine
rpm automatically to road speed during any shift sequence.
• The ESS transmission had no independent processing capability
and relied upon multiplexing to the engine electronics to operate.
• The end result was to make the shifting of a non-synchronized
manual transmission as easy as shifting a fully synchronized
transmission.
– As a three-pedal system, the main function of the clutch was to
break driveline torque at stall; that is, for starting and stopping
the vehicle.
– Auxiliary range shifts were automatic, reducing driver effort and
synchronizer damage.
– ESS featured a break torque switch that enabled the driver to
power upshift and downshift.
SureShift
• SureShift is a ZF Meritor three-pedal automated
transmission that uses joystick initiated shifts.
• The clutch pedal is used only to break driveline
torque at stall (starting and stopping).
• SureShift is currently available in 9- and 10-speed
transmissions.
• The electronics are J1939 networked to the chassis
data bus. The system is essentially a later version
of the ESS system.
FreedomLine
• The ZF Meritor FreedomLine transmission was the
first two-pedal system automated transmission
available for trucks.
• The driver can select either automatic or manual
modes of operation, but he has no direct control
over clutching.
• A self-adjusting system-actuated clutch is built into
the FreedomLine automated transmission.
• It is available in 12- and 16-speed versions.
• FreedomLine transmissions are networked into the
chassis data bus via a J1939 data link.
Mercedes-Benz AGS
• The automated transmission is an adaptation of the MercedesBenz six-speed, medium-duty, mechanical transmission that has
been around for a number of years.
• It is packaged into an aluminum housing and uses a two-pedal
system with a manual option mode.
• When operated in manual mode, the management electronics
prevent the driver from making a shift that could result in
driveline damage.
• It is networked to the J1939 data bus so that shift algorithms are
based in what is happening elsewhere in the engine and
drivetrain.
• Troubleshooting is accomplished using Freightliner ServicePro
software.
UltraShift
• The UltraShift automated transmission was
introduced by Eaton Fuller Roadranger in 2003 as
a two-pedal system. The initial release was a 10speed unit with an inertia brake.
• UltraShift uses a modular automation design that is
said to simplify service repair work. The clutch used
is a 15.5 inch, two-plate, ceramic button type with
coaxial springs.
• In common with all current automated
transmissions, the driver can option manual shifting.
• The Eaton Gen II software is programmed with
algorithms that prevent the driver from making a
shift that could result in driveline damage.
Urge to Move
• The latest innovation from Eaton Fuller is the addition of a fully
automated wet clutch to their six-speed AutoShift transmission
used in medium-duty applications.
• This converts their automated transmission into a two-pedal
system that handles similarly to an equivalent Allison automatic
transmission.
• To make the wet clutch perform much like an automatic with a
torque converter, Eaton’s wet clutch uses a creep feature known
as Urge-to-Move.
• Urge-to-Move loads a continuous 45 pounds-feet of torque to the
transmission through the wet-clutch pack so that the driver
senses engagement at any time the shift lever is in the drive
position.
• This system requires a cooler for the transmission fluid.
Summary (1 of 6)
• Automated standard transmissions use electronic
controls to adapt a standard mechanical
transmission for either semi-automated or fully
automated shifting. This technology allows the
driver to keep both hands on the steering wheel
during shifting and significantly reduces driver
fatigue.
• Automated transmissions can be divided into threepedal systems that use a clutch pedal and twopedal systems that eliminate the clutch pedal. All
automated transmissions use a clutch, but the
clutch is controlled by the system electronic control
unit (ECU).
Summary (2 of 6)
• The Eaton Fuller AutoShift transmission is based on
a standard Roadranger twin countershaft
mechanical transmission platform. AutoShift
electronics use two ECUs to perform logic
processing and output switching operations
required by the system.
• The AutoShift system manager ECU performs most
of the processing.
– It manages transmission functions and information,
interfaces with the chassis data bus, controls shifting
through its handshake connection with the transmission
controller, acts on driver command signals, performs
diagnostic self-checks, and logs fault codes.
Summary (3 of 6)
• The AutoShift transmission controller manages
shifting based on command signals received from
the system manager, monitors the input circuit
components physically located within the
transmission, exchanges speed and gear ratio
status data with the system manager, and provides
the system manager with diagnostic information.
• The AutoShift system manager ECU is located in
the shift tower assembly.
• The transmission controller ECU is located on the
left side of the transmission.
Summary (4 of 6)
• Shifts are effected by an electric shifter assembly that replaces
the gear shift lever in a standard Roadranger transmission. A
pair of reversing electric motors actuated by the transmission
controller precisely locates a shift finger in the shift block
recesses in the shift rails.
• The rail select motor is used to move the shift finger transversely
(side to side) with the objective of locating it precisely in the shift
recess of one of the three shift rails.
• The gear select motor moves forward and backward. After the
shift finger has been positioned over the correct shift rail, the
gear select motor is energized to move the rail into gear.
Summary (5 of 6)
• The means used by automated transmissions to
select gears is identical to that in a standard
transmission: shift finger movement first selects one
of the three shift rails, then slides that rail fore or aft.
• AutoShift transmissions perform self-diagnostic
tests and log fault codes when performance
parameters of any electronically monitored
component or system are out of specification.
Faults are broadcast over the chassis data bus.
• Fault codes can be displayed by the AutoShift
diagnostic (service) lights, or by either using a
handheld diagnostic EST or a PC with the
appropriate software.
Summary (6 of 6)
• The electronics are SAE J1939 compatible,
which permits multiplexing with other chassis
electronics systems.
• Most of the automated transmissions that
compete with the AutoShift system are similar
in terms of their principles of operation.