<VV> dragging clutch

djtcz at comcast.net djtcz at comcast.net
Sun Nov 25 10:44:12 EST 2007

Did the disk slide freely all along the input shaft splines? It must.

Can you rotate the engine to a position that the edge of the clutch disk is visible using the inspection mirror?  With the clutch pedal on the floor there should (must?) be A measureable/visible gap between the disk and flywheel or clutch or both. 

"With the clutch pedal completely depressed, a diaphragm (pressure plate, like Corvair ?) should have .030-.040 air gap between the disc and the flywheel"

If the disk is installed backwards I'd expect the gap to form between flywheel and disk.  

If the the disk was bent but otherwise installed correctly the release gap would be between the flywheel and disc in some areas and clutch and disk in others.  Either condition would cause some degree of drag.  When I worked in a balance shop we had balance mandrels that picked up the clutch disk ID (convenient, but not really correct datum for all types of SAE splines), and when spinning clutch disks for balancing many had visible runout that could sometimes be corrected/improved with relatively gentle persuasion.
I think placing the disk on the input shaft for a visual check while rolling the input shaft in wooden v-blocks might be quite revealing, and a useful low cost incoming inspection step.

Street type Clutch discs have a wavy spring under the linings to soften engagement.

I >>suppose<< a disk with a super wavy marcel spring and inappropriately fat fluffy new linings >>could<< drag when partially disengaged.  A disk with fat linings would have measured fat on the bench.  Here's a disk thickness report based on some number of field measurements - http://www.dalemfg.com/dale_032.htm

Loose or worn clutch linkage would be a much more likely and an externally repairable possibility.

I think I remember discovering I had installed the release fork with the sheet metal preload retainer on the wrong side of the throw out bearing groove a few times.  Thinking about it now, that might result in added useless "soft" travel bending the  retainer rather than the clutch springs, and probably causing the TO bearing to spin all the time and get noisy after a year or 2. 

Detecting a bent or installed-backwards disk requires an autopsy with some measuring tools at hand.

Dan Timberlake

-------------- Original message -------------- 
So in preparation for getting the car down and properly testing the system,
I removed all slack from the clutch release rod (in fact I compressed the
pressure plate as much as I could by hand in order to maximize the throw of
the clutch pedal).   I then took Greg Shaw's advice and removed the starterm
which allowed me to watch the throw out bearing at work (with the aid of a
mechanics mirror.)  All appears to be working  as it should be.  (Does
anyone know what the normal throw distance is for the bearing on the shaft?)
I then put the car in first gear and confirmed I could not turn the rear
wheels (by pushing on them simultaneously with my feet)  I then had my
daughter fully depress the clutch and found that, with some considerable
effort, I was able to turn the wheels, BUT I could also hear the clutch
rubbing on the pressure plate/flywheel.  (Am I right  in concluding from
these facts that my problem is unlikely to be a seized pilot bushing?) 

Given that my clutch release rod adjustment must have the throw out bearing
riding on the pressure plate fingers to begin with, and I can see the
bearing being pressed further into the pressure plate when the clutch pedal
is depressed, I can't figure out why there would still be so much
contact/friction with the clutch disk.   Could this simply be due to an
excessively thick clutch plate and I should continue on with the "on the
ground" burn in efforts?  Or does any of this dictate that I just cut to the
chase and drop the drive train (although I really am not sure what I would
be looking for).  I am hoping for the former, but willing to accept the


Thanks in advance for any thoughts.

Steve Brennan



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