Clutch Disc
Description: The clutch disc consists of a metal disc
covered with a frictional facing similar to brake shoes or pads. The lining is
made of a woven or moulded non-organic material that also contains particles of
soft metal such as aluminium or brass. This improves the strength of the lining
and a series of radial grooves in the lining's face enhances the grip between
the flywheel and the disc. A splined hub in the centre of the disc mates with
the transmission's input shaft, thereby providing a direct mechanical coupling
between the two. A group of torsional springs located between the clutch hub and
lining dampens driveline shock and vibration. The clutch disc is located between
the flywheel and pressure plate.
Purpose: The clutch disc transmits engine torque directly
to the input shaft of the transmission. The clutch disc, when coupled with the
pressure plate and flywheel, makes and breaks the flow of power from the engine
to the transmission.
Maintenance Tips/Suggestions: Since pressure to the clutch
disc is applied and released continuously throughout the course of normal
driving, the clutch disc lining will wear over time making it a normal wear
item. Clutch chatter is a common symptom that may indicate a worn clutch, but
this symptom could also be caused by oil leaking from the engine onto the clutch
assembly, a poor flywheel surface, damaged pressure plate release levers, a
sprung clutch disc hub and improper alignment between the engine and
transmission.
Another common clutch problem is clutch slippage. This can be caused by a
variety of factors such as a damaged pressure plate, worn, binding or
misadjusted linkage, incorrect clutch components, and even normal wear.
A dragging clutch is the least common symptom and is just the opposite of
slippage. Drag occurs when the clutch doesn't release at all, or releases only
partially. Clutch drag is usually caused by a worn, binding or misadjusted
clutch linkage. Drag can also be caused by air in the hydraulic clutch linkage,
damaged pressure plate fingers, and binding of the clutch disc on the input
shaft. To get to the heart of your car’s clutch problem, have a professional
technician road test your car to confirm the symptoms you’re experiencing. It is
the best first step of a proper diagnosis.
Clutch Linkage
Description: The clutch linkage is an arrangement of
mechanical and sometimes hydraulic components. A mechanical clutch linkage
usually consists of the clutch pedal, a series of linkage rods and arms, or a
cable. A hydraulic clutch linkage typically includes a clutch master cylinder
and reservoir, a hydraulic line and a slave cylinder. Hydraulic linkages have
become increasingly popular because they give the manufacturer the flexibility
to increase force at the clutch fork, with fewer space constraints compared to
mechanical linkages.
Purpose: The linkage transmits and multiplies the driver's
leg force to the fork of the clutch pressure plate. Whether the linkage is
mechanical or hydraulic, the linkage should have some sort of adjustment for
clutch play (a certain amount of slack in the clutch linkage).
Maintenance Tips/Suggestions: Check your owner’s manual to
find out if your car requires a periodic clutch adjustment. Many of today’s
models have self-adjusting clutches that automatically compensate for excessive
play in the clutch linkage. Symptoms of an improperly adjusted clutch or
problems with the clutch linkage may include a stiff clutch pedal, clutch
slippage, premature wear of the throw-out bearing, gear clash when shifting, or
a clutch that won’t release. Also, a clutch that may seem OK one minute, but not
the next may indicate a loose, worn or missing engine or transmission mount. A
qualified technician can quickly determine where the problem lies. Have the
clutch problem looked into as soon as possible, because a minor repair may be
all that’s required to prevent more serious problems.
Clutch Safety Switch
Description: The clutch safety switch, sometimes called a
clutch start or interlock switch, is an electrical switch connected to the
engine’s starting circuit.
Purpose: The clutch safety switch prevents the engine’s
starter motor from cranking the engine unless the driver applies the clutch
pedal. This eliminates the chance of cranking the engine with the transmission
in gear, which could cause sudden vehicle movement, especially if the engine
starts. In some cases, the clutch safety switch also serves a secondary purpose
-- it disables the cruise control if the driver applies the clutch with the
cruise control engaged.
Maintenance Tips/Suggestions: Not all cars are equipped
with a clutch safety switch, so check your owner’s manual for mention of this
safety device. Problems with the clutch safety switch may include a no-start
condition, starting with the clutch released and the transmission in gear, and
inoperative cruise control. If you suspect a problem with the clutch safety
switch or its adjustment, consult a professional service technician.
Continuously Variable Transmission (CVT)
Description: A Continuously Variable Transmission (CVT)
uses an arrangement of pulleys and bands to achieve an unlimited variation
between the highest and lowest ratios. Unlike conventional automotive
transmissions, CVTs do not employ a graduating arrangement of fixed gear ratios
to deliver power transmission. CVTs have seen spotty vehicle applications over
the years, but have staged a recent comeback due to improving and emerging
technologies.
Purpose: CVTs help the engine stay closer to its most
efficient operating range, which can help both performance and fuel economy.
CVTs may also offer manufacturers different economies of scale for transmission
manufacturing.
Maintenance Tips/Suggestions: CVTs require a different
maintenance regimen than conventional manual or automatic transmissions. Refer
to your car’s owner’s manual for specific recommendations for CVT
maintenance.
Flywheel
Description: The flywheel mounts to the engine's
crankshaft and transmits engine torque to the clutch assembly. The flywheel,
when coupled with the clutch disc and pressure plate makes and breaks the flow
of power from the engine to the transmission.
Purpose: The flywheel provides a mounting location for the
clutch assembly. When the clutch is applied, the flywheel transfers engine
torque to the clutch disc. Because of its weight, the flywheel helps to smooth
engine operation. The flywheel also has a large ring gear at its outer edge,
which engages with a pinion gear on the starter motor during engine cranking.
Maintenance Tips/Suggestions: Clutch chatter is a common
symptom that may indicate a poor flywheel surface or a worn clutch, but this
symptom could also be caused by oil leaking from the engine onto the clutch
assembly, damaged release levers, a sprung clutch disc hub, or improper
alignment between the engine and transmission. The face of the flywheel, the
area that contacts the clutch disc, is subject to "heat checking" which occurs
during excessive heat build-up between the clutch disc and flywheel. This is the
result of excessive slippage between the two. In many cases, the flywheel can be
resurfaced during a clutch replacement. To get to the heart of your car’s clutch
problem, have a professional technician road test your car to confirm the
symptoms you’re experiencing. It is the best first step of a proper diagnosis.
Pilot Bearing
Description: The pilot bearing sits in a hole at the end
of the engine’s crankshaft. Pilot bearings have three different designs:
1) roller bearing,
2) needle bearing, and
3) bronze bushing, which is actually more of bronze sleeve than a
bearing.
The bronze bushing and needle bearing are most common.
Purpose: The main purpose of the pilot bearing is to
provide a low-friction support for the end of the transmission’s input shaft.
Maintenance Tips/Suggestions: The pilot bearing does not
require routine maintenance, but should be replaced when clutch replacement
becomes necessary. In some cases, pilot bearings can wear excessively when
transmission-mounting bolts loosen. When this happens, the transmission’s input
shaft moves around excessively and puts abnormal strain on the pilot bearing. If
you suspect a problem with the pilot bearing or clutch, have it looked at
immediately by a qualified technician. Putting it off will only make the problem
worse.
Pressure Plate
Description: The pressure plate contains a clutch plate,
springs, cover and release fingers. This sub-assembly bolts to the flywheel,
with the clutch disc sandwiched in between. Although there are two types of
pressure plates, the spring-type and the diaphragm-type, the latter is used most
often.
Purpose: The pressure plate, as its name implies, applies
pressure to the clutch disc for the transfer of torque to the transmission. The
pressure plate, when coupled with the clutch disc and flywheel, makes and breaks
the flow of power from the engine to the transmission.
Maintenance Tips/Suggestions: Clutch chatter is a common
symptom that may indicate a worn clutch, but this symptom could also be caused
by oil leaking from the engine onto the clutch assembly, a poor flywheel
surface, damaged pressure plate release levers, a sprung clutch disc hub and
improper alignment between the engine and transmission.
Another common clutch problem is clutch slippage. This can be caused by a
variety of factors such as a damaged pressure plate, worn, binding or
misadjusted linkage, incorrect clutch components, and even normal wear.
A dragging clutch is the least common symptom and is just the opposite of
slippage. Drag occurs when the clutch doesn't release at all, or releases only
partially. Clutch drag is usually caused by a worn, binding or misadjusted
clutch linkage. Drag can also be caused by air in the hydraulic clutch linkage,
damaged pressure plate fingers, and binding of the clutch disc on the input
shaft. To get to the heart of your car’s clutch problem, have a professional
technician road test your car to confirm the symptoms you’re experiencing. It is
the best first step of a proper diagnosis.
Throw-Out Bearing
Description: The throw-out bearing, or clutch release
bearing as it's sometimes called, is located between the clutch fork and the
pressure plate fingers. The throw-out bearing only operates when the clutch
pedal is depressed; the bearing is not designed for continuous use.
Purpose: When the driver steps on the clutch pedal, the
throw-out bearing applies force to the fingers of the spinning pressure plate to
release the clutch. When the clutch pedal is released, the bearing sits idle and
does not contact the pressure plate fingers.
Maintenance Tips/Suggestions: The classic symptom of a
worn throw-out bearing is a whirring or growling sound when applying the clutch
pedal, which goes away when releasing the pedal. Premature wear of the throw-out
bearing can occur when there is insufficient clutch play, resulting in a
throw-out bearing that spins continuously. If the bearing fails, it may seize
and quickly wear the fingers of the pressure plate. The throw-out bearing does
not require routine maintenance, but should be replaced when clutch replacement
becomes necessary. Consult a professional technician to determine whether the
throw-out bearing or other parts of the clutch assembly need replacement.
Transaxle
Description: An aluminium or iron housing containing an
arrangement of bearings, synchronizers, shift forks, gears and shafts. The input
shaft receives engine torque from the clutch disc and the output shaft delivers
power to the driving wheels. On front wheel drive cars, the transmission and
differential are combined into a single housing called a transaxle.
Purpose: A manual transmission changes the engine’s speed
and torque in relation to the speed and torque of the drive wheels. This keeps
the engine’s output matched as close as possible to varying road speeds and
loads.
Maintenance Tips/Suggestions: Check your car’s owner’s
manual to find out when your car’s transmission might require a lubricant
change. The level of lubricant should also be checked at every oil change. Make
sure that any lubricant used for changes or for “top-off” meets the requirements
of the car manufacturer. This information is also in your owner’s manual.
Symptoms of faults inside the transmission may include difficulty when shifting
gears, grinding when shifting gears, a growling or whining noise with the
transmission in a certain gear range, and popping out of gear. Pinpointing
problems in the transmission is best left to a professional technician.
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