The T/E/L clutch is a very simple unit
with hydraulic system operating a cast steel clutch fork, throw-out
bearing and diaphragm-type pressure plate. Many unsufficient disengagement
problems commonly experienced with aftermarket and heavier clutches
can be traced back to three basic causes:
1) There's unsufficient pressure created
within the hydraulic system as result of air bubbles or leaks, incorrect
clutch master cylinder adjustment or its mulfunction or excessive wear
of the clutch lever of the pedal assembly.
2) Incorrect flywheel step height.
3) Unsufficient travel distance of the
throw-out bearing.
Since many heavier clutches such as the ACT2600 reguire higher than
stock pressure to fully disengage due to their heavier diaphragms, a
slight preload of the clutch (a few psi within the hydraulic system
with the clutch completely disengaged) is needed in order for the master
cylinder to be able able to create sufficient pressure to fully disengage
the diaphragm within its limited stroke.
Once the clutch pedal is depressed and
pressure within the hydraulic system created, the slave cylinder extends
and consequently pivots the clutch fork against the pivot ball. The
throw-out bearing travels forward, depresses the diaphragm of the pressure
plate and lifts its friction surface off the clutch disc. The maximum
travel distance of the throw-out bearing is realized once the recessed
back of the clutch fork reaches the bellhousing which acts as a stop.
At that point, the throw-out bearing should have traveled far enough
to fully disengage the pressure plate. A correctly adjusted clutch pedal
will reach this point while resting on the floor which consequently
creates the proper pressure within the hydraulic system. Goals to be
achieved:
1) Only as much as needed pressure within
the hydraulic system to fully disengage the clutch since excessive and
unnecessary pressure leads to master and slave cylinder seals failure.
2) The clutch pedal must reach the floor
at the same time (or a bit sooner) as the clutch fork reaches the bellhoising
stop.
3) The diaphragm of the pressure plate
must be compressed enough to fully disengage the clutch at that point.
1) Incorrect (less than 0.610") flywheel step height.
2) Pressure plate diaphragm fatigue, excessive wear or deformation.
3) Clutch fork or pivot ball excessive wear.
4) Excessively (too many times) machined flywheel.
There are only four ways to correct
the problem - beside replacing the faulty components:
1) Shim the flywheel toward the transmission.
2)
Shim the throw-out bearing.
3) Increase the recess of the back of the
clutch fork (not recommended).
4) Shim the pivot ball.
If you choose to shim the pivot ball to bring the throw-out bearing
closer to the pressure plate fingers while increasing the throw of the
clutch fork, be aware that 1/16" washer under the pivot ball results
in much greater distance of the throw-out bearing travel. If you shim
the pivot ball too much, the fingers of the pressure plate may start
hitting the clutch disc once the clutch fork reaches the bellhousing
stop. Also, the preload of the clutch must be adjusted accordingly (so
the clutch fork reaches the bellhousing stop right before or when the
clutch pedal reaches the floor).
