Clutch and Flywheel Wear Pattern

[QB93Z]

Last weekend we removed the clutch and flywheel from a low milage, 1991 ZR1 to correct a noise problem from the throwout bearing and/or the pilot bearing.

Upon removal of the clutch, I noticed an interesting wear pattern on the flywheel, the clutch and the clutch disc:

Here is the clutch pressure plate face:


Here is the flywheel surface:


Here is the clutch disc:


Notice that the inner third of the friction surrface shows a different pattern that the rest of the surface. There seems to be significant material transfer to the pressure plate and flywheel:

Clutch:


Flywheel:


The dual-mass flywheel internal dampers have failed and the relative motion of the parts is about 25 degrees with a "hard" stop at each end of travel.

The only other unusual thing we found was that the pilot bearing inside diameter is off center:


We replaced the flywheel, clutch, disc, throwout bearing, and the pilot bearing.

Any thoughts of the cause of the wear patterns?

Jim