General clutch diagnosis and solution

Clutch drags. It won't release completely and the transmission grinds when shifted

Possible diagnosis Likely solution
Linkage out of adjustment or binding Adjust or repair linkage
Release arm too long for the linkage system Determine the correct ratio (as per instructions above) and shorten the arm
Release arm sitckout angle incorrect Change the length of the release nearing, pivot or both, if necessary
Release arm hits bellhousing opening preventing full travel of the arm Grind clearance as necessary on the bellhousing
Engine is shifting on the motor mounts, wasting linkage travel Repair, rebuild or replace the motor mounts as necessary
Pilot bushing binding on the input shaft. Possibly damaged at installation or resulting from a misaligned bellhousing Replace the pilot bushing. Refer to the bellhousing alignment procedure in the Novak guide
Input shaft pilot is "bottoming out" in the crankshaft bore Shorten the input shaft by grinding or deepen the bore of the crank by drilling
Clutch disc hub is damaged or assembled incorrectly Replace the disc
Pressure plate or cover is warped Replace the pressure plate assembly
Excessive run-out at the face of the flywheel Check the crank flange for burrs and remove them, or reface the flywheel
Incorrect flywheel to crank hub bolts. The bolt heads are driving the disc Use the correct, special flywheel bolts
Clutch disc is installed backwards. The bolt heads are driving the disc Disassemble and turn the disc around
Clutch disc is too large. The edge of the disc is interfering with the pressure plate assembly Specify a smaller disc or turn down the edge of the existing unit
Clutch arm to throwout bearing retaining clip is tweaked on the bearing lip (progressive worsening) Replace throwout bearing if damaged and reinstall the arm and clips correctly


Clutch Slippage

Possible Diagnosis
Likely Solution
Linkage out of adjustment or binding
Adjust the linkage to create proper amount of slack in the system
Release bearing is too long, holding the clutch in a slightly disengaged position
Use a shorter release bearing. See the chart in the text
The friction surface on the flywheel, pressure plate or disk is glazed (usually from heat)
Resurfacing and replacement of clutch assembly
The clutch is too small and/or the spring load is too light
Use a larger clutch or a heavier spring. The former is often preferable. Extreme cases may require both
Oil on the clutch disc
Repair the oil leak (typically the engine rear main or oil pan if not the transmission from seal) and replace the disc
Broken or fatigued springs
Replace the pressure plate

Clutch chatters when engaging

Possible diagnosis Likely solution
Damper springs in the clutch disc hub or the marcel spring between the facings is fatigued Replace the clutch disc
Friction surface on the flywheel or pressure plage is glazed from the heat Resurface or replace as necessary
Clutch disc is running out on the input gear (hub problem) Replace the clutch disc
The flywheel or pressure plate surface is running out Reface or replace as required
Oil on friction surfaces Repair the oil leak (typically the engine rear main or oil pan if not the transmission from seal) and replace the disc. Avoid parts contamination upon reassembly
Linkage works erratically Inspect the linkage, paying special attention to the holes in each lobe. Repair or change the linkage as required
Play in the motor mounts allowing for shifting of the powertrain, relative to the linkage Change or repair the motor mounts


Pedal pulsates when pushed to floor (3-finger coil spring type only)

Possible diagnosis Likely solution
Clutch is over-releasing and the release fingers are hitting the disc hub damper springs Reduce linkage travel (see above text)


Pedal pulsates at start of release

Possible diagnosis Likely solution
Flywheel run-out Check for burrs on clutch and flywheel mounting flanges
If a three-finger type, fingers may not all be the same height Have the pressure plate readjusted by a rebuilder or replace the pressure plate
Excessive clearance between release bearing and retainer Replace the retainer or on mismatched parts, sleeve retainer up to the release bearing size, plus slip fit


Noise; clicking or rattling at idle RPM with the pedal released

Possible diagnosis
Likely solution
Broken spring(s) Replace the pressure plate


Noise; whirring or grinding when clutch is released (pedal depressed)

Possible diagnosis Likely solution
Failing clutch release bearing Replace


Noise; chattering or "buzzing" when clutch is released

Possible diagnosis Likely solution
Excessive pilot bushing to input gear clearance. Often resultant of bellhousing misalignment Replace pilot bushing. Clearance should be .001 to .004


Pedal is hard to push and hold down

Possible diagnosis Likely solution
Improperly set-up linkage system Change as required (see text)
Pressure plate spring load excessive for linkage Reduce spring load, or, if high pressure clutch is required then modify the linkage to give the minimum travel that will still release (i.e., provide the required .025 air gap) and leave a finger clearance of 1/16"