The flywheel mounts to the engine's crankshaft and transmits engine torque to the clutch assembly. The flywheel, when coupled with the clutch disc and pressure plate makes and breaks the flow of power from the engine to the transmission.
The flywheel provides a mounting location for the clutch assembly. When the clutch is applied, the flywheel transfers engine torque to the clutch disc. Because of its weight, the flywheel helps to smooth engine operation. The flywheel also has a large ring gear at its outer edge, which engages with a pinion gear on the starter motor during engine cranking.
Clutch chatter is a common symptom that may indicate a poor flywheel surface or a worn clutch, but this symptom could also be caused by oil leaking from the engine onto the clutch assembly, damaged release levers, a sprung clutch disc hub, or improper alignment between the engine and transmission. The face of the flywheel, the area that contacts the clutch disc, is subject to "heat checking" which occurs during excessive heat build-up between the clutch disc and flywheel. This is the result of excessive slippage between the two. In many cases, the flywheel can be resurfaced during a clutch replacement. To get to the heart of your car’s clutch problem, have a professional technician road test your car to confirm the symptoms you’re experiencing. It is the best first step of a proper diagnosis.