GMC 4000 Series Service Manual page 470

Total lift readings should be .055" to .075" .
NOTE: Excessively high readings indicate
that the diaphragm spring is being over-stressed
which may eventually cause loss of load and result
in slippage.
SYMPTOMS AND PROBABLE CAUSE
SLIPPING
1. Improper adjustment.
2. Oil soaked clutch disc.
3. Worn splines on transm ission drive gear.
4. Lining loose on clutch disc.
5. Warped pressure plate or engine flywheel.
GRABBING
1. Oil on disc lining.
2. Worn splines on transm ission drive gear.
3. Loose engine mountings.
4. Warped pressure plate or engine flywheel.
RATTLING
1. Weak retracting springs.
2. Release fork loose on ball pivot stud.
NOISY
1. Worn clutch release bearing.
PEDAL SPONGY
1. Air in clutch hydraulic line.
EXCESSIVE PEDAL TRAVEL
1. Leaking slave cylinder line.
2. Fluid low in hydraulic master cylinder.
3. Clutch master cylinder push rod lever loose
or not properly adjusted.
CLUTCH PEDAL RELEASES CLUTCH BUT
PEDAL GRADUALLY TRAVELS DOWNWARD
1. Clutch master cylinder leaks past primary cup.
2. External leaks.
G M C S E R V I C E M A N U A L
checke driven disc with clutch pedal depressed (it
should spin freely with transmission in neutral).
"Clutch Troubleshooting."
CLUTCH TROUBLESHOOTING
HYDRAULIC CONTROLS
If above measures fail to correct the trouble,
NOTE: If trouble still
PROBABLE REMEDY
1. Adjust slave cylinder travel clearance or if
control is of link type, make adjustment at
release fork or lever adjustment rod.
2. Install new disc.
3. Replace drive gear.
4. Install new disc.
5. Replace pressure plate or flywheel.
1. Install new disc.
2. Replace drive gear.
3. Tighten or replace engine mountings
4. Replace pressure plate or flywheel.
1. Replace springs.
2. Check stud and retaining spring and if
necessary, replace.
1. Replace release bearing.
1. Bleed clutch slave cylinder.
1. Tighten or replace line.
2. Fill cylinder to 1/2" below top of reservoir.
3. Adjust length of clutch push rod under dash.
1. Overhaul master cylinder.
2. Tighten all line fittings and check for leaks
in line.
Sec. 7E
Page 459
CLUTCHES
exists, refer to