Flywheels are precisely machines, (usually) heavy discs of metal with a ring gear attached around the edge. They serve a few purposes: First, they couple the engine to the tranmission via a clutch. Second, they allow for some stabilization of the engine as they carry momentum due to their weight. Finally the ring gear around the edge provides a location for the starter gear to engage and crank the engine when starting. Lightweight flywheels are sometimes used in performance applications to allow for quicker acceleration, and flexplates are used in place of a flywheel on vehicles with automatic transmissions to couple the engine to the transmission via a torque converter.
A flywheel may need replaced if it has cracked or somehow been thrown out of balance. The ring gear being damaged is another example of why a flywheel might need to be replaced.
Replacing a flywheel will involve removing the engine or transmission to access the studs necessary for removal.
We stock and sell a wide variety of quality flywheels from these manufacturers: