Often a thorough inspection of the clutch disc can indicate the exact cause of failure. For example, if the hub is uniformly broken away from the disc, a defective or missing pilot bearing could be the cause. This would result from improper alignment of the transmission to the engine.
Although the disc must be removed for a complete inspection, you can quickly inspect it by removing the flywheel inspection cover. Look for signs of oil and metal or lining materials on the inspection cover or bell housing. Evidence of any of these indicates that the disc should be replaced. If the linings are oil soaked, repair the oil leak before installing the new disc. Replace any disc that shows signs of overheating, indicated by a blueing of the steel disc backing or glazing of the linings.
As noted before, most clutch discs contain asbestos. Asbestos has been found to cause cancer and is therefore hazardous to your health. Always follow the recommended safety procedures when working with asbestos. Never blow out clutch dust with compressed air or breathe in clutch dust. Wash hands immediately after handling clutch dust, especially before eating.
If the disc passes these checks, inspect its torsion dampener springs, which dampen or cushion the input shaft and drive train from harsh engagement when the clutch is applied.
Carefully inspect the disc's torsional coil springs.
These springs are located between the friction facing and the splines of the input shaft. Try to rotate the dampener springs with your finger. They should rotate, but not easily, replace the disc. Usually a clutch disc used for more than 50,000 miles that is removed for other vehicle work should be replaced, regardless of its condition. The time and labor saved by replacing the disc will benefit the customer.