If the pedal is very hard to work after a new pressure
plate assembly is installed, the pressure plate apply springs
may be stronger than necessary. This is very common
when a heavy-duty or competition (racing) pressure plate
is installed. Return springs that are too heavy might be
responsible for hard pedal effort. Remember, as you
depress the clutch pedal, you are working against return-
spring tension.
In-Car Clutch Service
Clutch service commonly requires the removal of
major components, such as the drive shaft assembly, trans-
mission, and clutch assembly. However, certain clutch
problems can be attended to without removing these
major components. This type of service is categorized as
in-car service. Clutch repairs that fall into this category are
clutch adjustment and linkage repair or replacement.
Procedures are given in this section.
Clutch Adjustment
Clutch adjustment involves setting the correct
amount of free play in the clutch linkage. Too much free
play can cause clutch drag, preventing the clutch from
ever fully disengaging. In this case, the power flow is not
completely cut off from the clutch and the engine could
continue to propel the vehicle. Too little free play can
cause the clutch to slip. In this case, the throwout bearing
rotates continually as it contacts the rotating pressure plate
release levers or fingers, and it quickly wears out. With
enough pressure on the levers or fingers, the clutch slips,
overheats, and becomes damaged.
No matter what type of clutch linkage is used, the free
play can be checked by pushing the clutch pedal with your
hand. Refer to Figure 7-5 and the next few paragraphs for
the proper procedure.
Begin with the pedal in a fully released position—that
is, with the pedal all the way up. Start pushing down on
the pedal. The pedal should move easily for about 1″
(25 mm). In this span, the only pressure you are working
against is that of the return springs. Past this point, the
pedal becomes harder to push. This is where the throwout
bearing contacts the pressure plate release levers or
fingers, and you are working against the force of the pres-
sure plate apply springs.
The distance that the pedal moved from the fully
released position until it became hard to push is the free
play. All vehicle manufacturers specify the proper
amount of clutch free play. Free play is adjusted at some
place on the clutch linkage. On many vehicles, the
clutch has a self-adjusting feature that automatically
adjusts free play whenever the clutch pedal is
depressed.
Note: A slipping clutch that is badly worn
or damaged cannot be repaired by adjust-
ment. If adjustment does not stop clutch
slipping, or if enough free play cannot be obtained
(indicating worn parts), the clutch assembly must be
removed and worn parts must be replaced.
Rod-and-lever linkage adjustment
A rod-and-lever linkage is a series of links, levers, and
rods connecting the clutch pedal to the clutch fork.
Adjustment is usually provided by a threaded rod that
passes through a pivot block, Figure 7-6 and Figure 7-7.
An adjustment device is located on the linkage at the
clutch fork.
To adjust a rod-and-lever linkage, measure the actual
amount of free play at the clutch pedal and compare it to
specifications. Use a ruler to make an accurate measure-
ment. If the specifications are not available, 1″ (25 mm) of
free play is usually close. Before attempting to make the
adjustment, check that the linkage is not worn excessively.
A loose, sloppy linkage cannot be satisfactorily adjusted.
Next, for the single-locknut adjuster, loosen the lock-
nut that holds the threaded rod to the pivot block. Turn the
rod until the proper free play is obtained at the clutch
pedal and then retighten the locknut. For the double-lock-
nut adjuster, loosen the one locknut, depending on which
way the adjustment is to be made. Then, turn the other
locknut in the same direction, advancing the pushrod until
132 Manual Drive Trains and Axles
Freeplay
Ruler
Maximum
pedal
position
Resistance
begins
Throwout
bearing contacts
pressure plate
assembly
Firewall
or bulkhead
Floorboard
Figure 7-5. Free play can be measured using a ruler. The
amount of free play should match the manufacturer’s specifica-
tions. A general check can be made by observing the pedal
movement. The throwout bearing first contacts the pressure
plate assembly at the point where resistance is first felt when
pressing on the pedal.