CCAS 3381
AUTOMOTIVE SKILL I
OBJECTIVES
 To
understand the operational
principles and basic mechanisms
of transmission system
Lecture – 1 hour
Workshop – 1 hour
TRANSMISSION SYSTEM (1)
Manual transmission system
Manual
gear box
Manual
gear knob
Manual
gear box
5-speed manual gearbox
TRANSMISSION SYSTEM (2)





Green shaft (input shaft) & gear
turn at the same rpm as the
engine
Red shaft (layshaft) & gears are
directly connected to the input so
it spins when input shaft spins
Yellow shaft (output shaft) is
splined shaft connected directly
to drive shaft through differential
to drive wheels (If wheels are
spinning output shaft spins)
If engine is off with car coasting
output shaft turns inside blue
gears (blue gears & layshaft are
motionless)
Collar connects one of two blue
gears to output shaft via dog teeth
TRANSMISSION SYSTEM (3)




Moving knob forward & backward
moves collar to engage the gears
Reverse gear is handled by a
small idler gear (purple)
Importance of transmission:
– Engine redline (max. rpm
above which engine explodes)
– Engines have narrow rpm
ranges (horsepower & torque
are at their maximum)
Synchronizers allow collar & gear
to make frictional contact before
dog teeth make contact (collar &
gear synchronize their speeds
before teeth need to engage
TRANSMISSION SYSTEM (4)
A car engine spins all
the time & car wheels
don't (to stop without
killing the engine
wheels, engine needs
to be disconnected
from the engine)
 Flywheel connected to
engine
 Clutch plate connected
to the transmission

Pressure plate
Clutch plate
TRANSMISSION SYSTEM (5)
Springs force on pressure plate
 Clutch plate springs - isolate
transmission from shock of clutch
engaging
 Friction material on the clutch disc wears
out (similar to the friction material on the
pads of a disc brake pads/shoes of a
drum brake; clutch slips & lost of power)
 Driver who slips the clutch a lot will wear
out clutch a lot faster
 Worn throw-out bearing (rumbling noise
whenever the clutch engages)

TRANSMISSION SYSTEM (6)

Other clutches:
– Automatic transmission with several
clutches used to engage and disengage
various sets of planetary gears
– Car air conditioning compressor with
magnetic clutch
– Engine-driven cooling fan with
thermostatically controlled viscous
clutch
TRANSMISSION SYSTEM (7)

Ideally, transmission should be
flexible in its ratios that engine runs
at its single, best rpm value
(continuously variable transmission CVT) – Honda City
TRANSMISSION SYSTEM (8)


Manual transmission checklist:
– Check for oil leaks (RM5000 new Kancil
gearbox)
Manual transmission test drive
– With transmission lever in neutral,
parking brake applied & engine idling,
listen to any loud noises when clutch
pedal pressed or released
– Try to drive the car at all speeds one by
one - every speed should shift smooth &
easily without any noises or jerks
TRANSMISSION SYSTEM (9)

Manual transmission test drive
– While driving at 2nd or 3rd gear, try to
press down sharply on the accelerator
pedal for an instance (clutch should
not slip, any slipping i.e., engine rpm
increases but speed remains the
same clutch most likely has to be
replaced)
– Try to drive with acceleration &
deceleration (there should be no
whining or humming noise under any
condition with all gears should shift
easily & noiselessly)
TRANSMISSION SYSTEM (10)
Automatic transmissions:
– no clutch pedal
– no gear shift
 Automatic transmission (gearbox plus
torque converter) – like manual
gearbox & its clutch

Torque
converter
Auto
gearbox
Auto transmission system
TRANSMISSION SYSTEM (11)
In automatic transmission, same set of
gears produces all of the different gear
ratios (planetary gearset)
 Planetary gearset

– A set of bands to lock parts of gearset
– Three wet-plate clutches to lock other parts
of gearset
– Hydraulic system controlling clutches &
bands
– Large gear pump to move transmission fluid
around

Planetary gearset has 3 main parts:
– Sun gear
– Planet gears & planet gears' carrier
– Ring gear
TRANSMISSION SYSTEM (12)
TRANSMISSION SYSTEM (13)
Each of these 3 parts can be input,
output or stationary (determines gear
ratio)
 First Gear - 2.4:1
 Second Gear - 0.67:1
 3rd gear - 1:1 ratio in 3rd gear
 Overdrive has a faster output speed than
input speed (output of engine goes
straight to transmission)
 Ratio = 1 / (1 + S/R) = 1 / ( 1 + 36/72) =
0.67:1 (an engine turning at 2000 rev/min
output speed is 3000 RPM allowing cars
to drive at freeway speed while the
engine speed stays nice and slow

TRANSMISSION SYSTEM (14)



Differentials (where engine power, in most
cars, makes its last stop before spinning
the wheels)
– Aim engine power at the wheels
– Act as final gear reduction in the car
(reduce rotational speed of transmission
one final time before it hits the wheels)
– Transmit power to the wheels while
allowing them to rotate at different
speeds during turning
Device that splits engine torque two ways,
allowing each output to spin at a different
speed
Differential is found on all modern cars &
trucks, and also in many all-wheel-drive
(full-time 4WD vehicles)
TRANSMISSION SYSTEM (15)
Differential
TRANSMISSION SYSTEM (16)
Final drive ratio (gear ratio in the
differential)
 Open differential always applies the
same amount of torque to each wheel
 Two factors determining how much
torque can be applied to the wheels:
– equipment
– traction
 Dry conditions - torque
applied to wheels
limited by engine &
gearing

TRANSMISSION SYSTEM (17)
In low traction - amount of torque limited
to greatest amount that will not cause a
wheel to slip under those conditions (if
you give the car more gas after the
wheels start to slip, the wheels will just
spin faster – problem with open
differentials
 Limited slip differential (LSD) –
positraction - allows more torque to be
transferred to the non-slipping wheel

TRANSMISSION SYSTEM (18)

Automatic transmission checklist
– Place your car at a level surface, start
engine, set transmission lever to "P“
& let engine idle
– Pull transmission dipstick
– Wipe it off with a lint free clean
rag/tissue
– Insert it back carefully all the way
down into its place
– Pull again & check fluid level
TRANSMISSION SYSTEM (19)

Automatic transmission
checklist
– Pull again & check fluid
level
 Engine
cold fluid within
"COLD" marks
 Engine hot fluid level at
upper end of "HOT"
mark (top it up if it is
lower)
 Check fluid condition
also: too black & a burnt
smell -transmission may
not last
TRANSMISSION SYSTEM (20)

Automatic transmission
checklist
– Pull again & check fluid
level
 There
should not be any
metal filings or black
flakes

Topping up transmission
fluid
– Use only specified
transmission fluid (check
your manual)
TRANSMISSION SYSTEM (21)

Topping up transmission
fluid
– Add a small amount of
fluid through dipstick
pipe as shown in the
image & do not overfill it
– Wait for a few minutes
to let fluid to flow down
– Start engine & check
level again
TRANSMISSION SYSTEM (22)

Transmission maintenance
– Most of transmission troubles start
after overheating
 Under
heavy load
 Continuous stop & go traffic in hot
weather
 Racing
 Accelerating too hard to free the car
 At higher temperatures transmission fluid
burns loosing its lubricating qualities &
becomes oxidized leaving deposits all
over inside
 Exposed to heat rubber seals & gaskets
inside transmission become hardened
causing leaks
TRANSMISSION SYSTEM (23)

Transmission maintenance
– Most of transmission troubles start
after overheating
 Metal
parts warp & loose their strength
– Poor design
– After being rebuilt by inexperienced
technician
– Harsh driving
– Too low or too high transmission
fluid level
– Wrong transmission fluid type
TRANSMISSION SYSTEM (24)

How to prevent the transmission from
damage
– Always check your parking space for
leaks (get it fixed before it caused
something serious)
– Once in a while check transmission
fluid level & condition
– Use only same type of the
transmission fluid as specified in
owner's manual
– Never shift to “R” or “P” until car
comes to a complete stop
TRANSMISSION SYSTEM (24)

How to prevent the transmission from
damage
– Never shift from “P” mode when
engine rpm is higher than normal idle
– Always hold a brake down when
shifting from “P”
– Do not tow with drive wheels on the
road
– Go to transmission shop when you
experience any problems with your
transmission such as leaks, noises,
problems with shifting, etc.
TRANSMISSION SYSTEM (25)
ATF (owner’s manual)
 Fluid change (40,000 km or so)
 Good conditions – clean & odorless

 Transmission
screen/filter
THE END
IQ + EQ + SQ = TQ*