Clutch Vibration
Some clutch defects can result in a vibration that can
be felt inside of the vehicle while the clutch is fully
engaged. This clutch vibration varies with engine speed. It
differs from chatter, which occurs when the clutch is in the
process of being engaged or disengaged. Often, clutch
vibration is accompanied by noise; however, the noise is a
secondary symptom.
Several checks must be made to find the source of the
vibration. This is to determine if the problem is clutch
vibration or vibration from another source.
Vibration with the vehicle moving may be caused by
the engine or any part of the drive train. To narrow down
the possibilities, determine when the problem occurs. If the
vibration occurs only when the vehicle is moving, the prob-
lem is probably not clutch related. Even so, you should
check the bolts that secure the clutch housing to the engine
and to the transmission just to make sure they are not loose.
Thoroughly check the drive shaft assembly, drive axles, and
engine mounts. Closely inspect conventional or constant-
velocity joints for any signs of wear. In rare cases, internal
problems in the transmission or differential or the transaxle
may cause vibration while the vehicle is moving. (Refer to
later chapters related to these components.)
If the vibration also occurs with the vehicle stopped
(transmission in Neutral), the source of the problem is
related to the clutch or the engine. Check the engine for a
dead cylinder or other internal problem. Vibration result-
ing from excessive crankshaft endplay can be identified by
disengaging the clutch. Pressure from the throwout bearing
will push the flywheel and crankshaft forward, taking up
the endplay and eliminating any corresponding vibration.
If the engine is okay, look for problems indirectly
related to the clutch. First, however, check the clutch hous-
ing where it attaches to the engine and to the transmission.
Check the front bearing retainer where it attaches to the
transmission. Ensure all bolts are tight, Figure 7-3. Look at
the transmission front bearing as a possible cause of vibration.
Inspect the clutch assembly if the previously men-
tioned checkpoints have failed to identify the source of
vibration. There are two general sources of clutch vibration:
A part associated with the clutch assembly is out of
balance. The parts that are heavy enough to be seri-
ously unbalanced are the flywheel and pressure plate.
A balance problem is often found after new parts are
installed or the flywheel is resurfaced. The chance of
a flywheel or pressure plate becoming seriously
unbalanced after long use is slight.
A part associated with the clutch assembly is loose or
broken. Check attaching bolts of the clutch assembly.
The flywheel attaching bolts (flywheel-to-crankshaft
bolts) may be loose on the crankshaft, or there may be
dirt or metal burrs between the crankshaft flange and
flywheel. This causes misalignment of the flywheel.
When this happens, the clutch usually has other symp-
toms. The clutch may slip or make a knocking noise.
Clutch Explosion
A clutch explosion occurs when clutch components fly
apart due to centrifugal force. Major causes of clutch explo-
sions are excessive clutch rpm, severely unbalanced compo-
nents, and loose pressure plate fasteners. A clutch explosion
destroys all clutch components and often breaks the clutch
housing. A clutch used for racing will often have a scatter
shield installed over the clutch housing. This keeps flying
clutch components from entering the passenger compartment.
Abnormal Noise
Often, the clutch is blamed for a noise when some
other component is at fault. Any vehicle component can
become noisy under the right conditions. An abnormal
noise in the clutch can usually be singled out by applying
or releasing the clutch pedal. If the clutch is the source of
the noise, this will have some effect on the noise being made.
Rumbling, squealing, whirring, or grinding noises can
be caused by a defective transmission front bearing,
throwout bearing, or pilot bearing. A defective transmis-
sion front bearing will commonly make noise as the clutch
drives the input shaft, whenever the clutch is engaged. A
defective throwout bearing makes noise as the bearing is
applied. A noisy pilot bearing is usually heard when the
clutch is disengaged completely. It will not usually make
noise when the clutch is engaged, since the crankshaft and
input shaft are turning at the same speed, Figure 7-4.
Follow these procedures to isolate defective bearings:
1. While depressing the clutch pedal, start the engine
and leave it running. With the transmission in
Neutral, release the clutch pedal, taking your foot
completely off the pedal. Any noise that you hear
upon engaging the clutch will likely be coming from
the transmission front bearing.
130 Manual Drive Trains and Axles
Clutch housing
to engine
Clutch cover
to flywheel
Flywheel
to
crankshaft
Loose bolts are often a
source of vibration
and noise
Transmission to
clutch housing
Bearing
retainer to
transmission
Clutch
fork ball
Figure 7-3. Note places where bolts can loosen, causing
vibration (and noise). Often, bolts can be tightened to solve the
problem. Occasionally, the vibration will damage other parts
before the bolts are tightened.