Clutch kit installation and troubleshooting.
SUNBURY BRAKES ONLINE
Clutch Replacement Guide
Always replace the complete clutch i.e. Cover Assembly, Driven Plate
& Release Bearing.
Ensure that the correct parts are obtained, check against the
original units before fitting.
Place the driven plate inside the cover assembly pressure plate the
correct way round to ensure that no fouling occurs between the two
components.
Always use a clutch alignment tool.
Never allow the weight of the gearbox to hang on the clutch
components.
- Check the spigot bearing thoroughly for excessive wear and replace
if necessary.
- Examine all components for signs of oil contamination, check and
replace if necessary engine and gearbox oil seals.
- Examine the old clutch plate splines for signs of excessive wear or
damage; this may indicate previous gearbox misalignment.
- Check the flywheel for run-out, scoring or cracking and excessive
wear, abnormal and excessive clutch plate wear will occur unless this
corrected. If machining of the
flywheel is undertaken ensure that the same amount of material is removed from
both friction and mounting surfaces.
Flywheels with excessive wear should always be
replaced.
- Ensure that the clutch release mechanism operates freely, examine
all release bearing mounting components (clutch release arm, cross shaft,
bushes bearings etc) for excessive wear or damage. Replace all substandard
parts.
- Ensure all contact surfaces are in good condition, and that oil or
grease is not allowed to contaminate the contact surfaces. Always remove any protective coating
that may be applied to the clutch cover pressure plate.
- Ensure that the driven plate is not damaged prior to fitting,
lightly grease the spline and ensure that the driven plate slides freely on
the gearbox spline. Take care not
to damage the spline on fitting.
- Ensure that the driven plate is fitted the correct way
round.
- Use an alignment tool to position the driven plate centrally during
fitment, do not remove the tool until all the cover assembly bolts have been
tightened.
- When re-fitting the cover assembly to the flywheel the mounting
bolts must be tightened diagonally and not in rotation, ensure that the cover
is located correctly onto the dowels and that any alignment marks or slots are
matched correctly.
- Before re-fitting the gearbox ensure that all gearbox dowels are in
place and that they are not excessively worn. Ensure that any dowel bolts are
replaced in the correct location.
- When offering the gearbox up to the engine take care not to damage
the diaphragm fingers, release levers or release plate with the gear ox input
shaft.
- Ensure correct release bearing/clutch pedal adjustment, ensure
correct pre-load with constant running types. Always re-set any self adjusting
mechanisms that may be fitted.
- Check the condition of engine and gearbox mountings, replace if
necessary. Ensure there is
no excessive backlash in the universal joints or the rear
axle.
- Check the condition of hydraulic systems and replace substandard
parts.
- Check the condition of the clutch cable and ensure that is has not
stretched or frayed at any point, replace any substandard
parts.
The Clutch System Components and Common causes of
Failure.
Cover Assembly.
Damage of the diaphragm fingers by the gearbox input shaft during
installation and over stroked diaphragms are common causes of cover assembly
malfunctions. Ensure when
re-fitting the gearbox that this is carried out without damaging any of the
clutch components. To avoid
over stroking of the diaphragm, clutch adjustment should be checked and set
according to manufacturer’s specification.
Before leaving the production facility all cover assemblies are checked
for clamp loading, pressure plate lift and diaphragm run-out utilizing test
equipment.
Clutch Plate.
Clutch driven plates can be become distorted during transit or more
commonly during installation by ‘hanging’ of the gearbox on the drive
shaft. The risk of distortion can
be minimized by the use of an alignment tool and ensuring that the gearbox is installed without banging on the
clutch units. All driven plates are
individually inspected before leaving the factory and tested for run-out and
overall consistency of effective thickness using specially designed spin test
machines. In house computerized
evaluation equipment is available to measure (in both drive & overrun
positions) the torsional damping characteristics of the driven
plate.
Release Bearing.
Although it is not possible to fully check the operation of the
release bearing when it is removed, it is false economy to re-use the old
bearing as this often results is premature clutch failure. Therefore we recommend that it is always
replaced. Refitment of the old
component can also give excessive bearing noise and abnormal diaphragm
finger/release lever wear. The
bearing carrier should slide freely on the bearing quill, apply recommended high
temperature grease sparingly.
Clutch Cables.
It is recommended that clutch cables are replaced when clutch
components are renewed. Cables
often stretch beyond adjust limits resulting in non clearance. Ensure that the correct cable is fitted
and adjusted in accordance with the manufacturer’s
specification.
Flywheel.
The flywheel is often ignored during clutch replacement but should
always be checked before refitting new clutch components. Uneven facing wear on the flywheel side
of the drive plate can indicate severe flywheel wear, usually observed as a
badly grooved mating surface. Hot
spots and thermal cracks indicate the clutch has been running at high
temperatures. Any marking or
grooves on the mating surface should be removed or if excessive the flywheel
should be replaced. If
the flywheel is to be machined the original overall dimensions must be
maintained. The cover assembly
mounting flange must be machined down by the same amount as the contact surface
of the flywheel. The opportunity
should be taken to check the flywheel ring gear.
Spigot Bearing/Bush.
The spigot bearing can cause severe damage if worn as it allows the
gearbox to ‘float’. This can result
in excessive noise and misalignment leading to damage of the clutch
components. A worn spigot bearing
can cause unbalance resulting in vibration. It is good practice to replace the
spigot bearing/bush during clutch replacement.
Engine/Gearbox Oil Seals.
Leaking oils are a major cause of clutch failure, allowing
contamination of the clutch components.
A small amount of
contamination will affect the efficient operation of the clutch. Always check for traces of oil and
replace any suspect oil seals.
Release Fork/Release Mechanism.
A substantial amount of the clutch release stroke can be lost if wear
on the release mechanism is not corrected.
All parts such as release fork, cross arm, bushes, pivot blocks/pins
should be checked and replaced if any wear is located. Always ensure the free operation of the
linkage.
Release Bearing Housing
Wear on the side of the housing can affect the release bearing travel
causing grab or chatter of the clutch and off center release bearing contact
with the diaphragm. Ensure that the
housing is centered and concentric with the gearbox input
shaft.
Engine & Gearbox Mountings.
Worn or damaged parts can cause vibration and shudder, often it is
taken for clutch malfunction.
Components showing any signs of wear or damage should be
replaced.
Hydraulic Systems.
Inefficient operation of the clutch and non-disengage problems can be
caused by old, insufficient or air impregnated hydraulic fluid. Check operation of hydraulic components
such as master and slave cylinders, examine for leaks and replace substandard
parts. Flush the system and bleed
after clutch replacement.
Automatic Adjust Mechanisms.
Faulty auto adjust systems can cause excessive clutch slip, diaphragm
wear and non engage problems. When
these systems become inefficient it may be possible to replace with a manual
adjustment. Ensure that cables are
de-adjusted when new components are fitted and reset to vehicle manufacturer’s
specifications.
Clutch Adjustment.
As there are many differing specifications for adjustment always
refer to vehicle manufacturers instructions when setting this. Some vehicles require the release
bearing to run in constant light contact with the cover assembly diaphragm,
where others demand significant free play.
Overall clutch adjustment is critical in obtaining efficient operation of
the clutch, incorrect adjustment can lead to clutch slip, overheating, excessive
wear and release carrier contact with the diaphragm. These faults cause abnormal wear, broken
components and premature clutch life.