The flywheel in a car has several purposes. Its main purpose is to store energy to provide momentum and keep the crankshaft turning. It also helps balance the rotating assemblies and smooth vibrations transmitted to the drivetrain. It transmits energy smoothly to the transmission, providing power to perform its work.
The transmission receives power from the engine through the clutch assembly. The clutch disk is covered in friction material similar to that found on brake shoes. When the disk is pressed against the flywheel by the pressure plate, a high amount of friction allows it to grip the surface, and rotating energy is applied to the transmission to make your car move down the road. When the disk lining begins to wear, it loses this ability to grip.
As a result, it will begin to slip, and over time, it will polish the mating surface, making the slipping worse. The friction from this slippage causes a great deal of heat. There is so much heat produced, in fact, that it will effectively “heat treat” the metal surface. This can damage the surface, causing it to become too hard. In some cases, cracks and blisters can develop in the surface of the flywheel due to this increased hardness. This condition is often referred to as “hot spots” on the surface. Hot spots occur because the heat is applied unevenly. Consequently, the hardened places are not evenly distributed across the surface.
For these reasons, whenever the throwout bearing, pressure plate or disk is replaced, manufacturers also recommend the flywheel undergo a “resurface”. During a resurface, the part is fixed to a machine that cuts a very thin layer of metal off the surface. This process exposes fresh metal to the disk, and provides a slight roughening of the surface. This will improve grip over the previously polished surface. The amount of metal removed during a resurface depends on the depth of the hot spots.
It is a good idea to stop using the vehicle when the clutch starts to slip, and have it repaired immediately. If too much metal has to be removed during the resurface, the part will be too thin, and it will no longer meet manufacturer’s specifications for proper operation, weight and safety.
Some symptoms of problems in the clutch assembly include:
Since the flywheel is attached to the engine’s crankshaft, the engine and transmission must be separated to remove the flywheel for a resurface. In many vehicles, this will mean the engine must be removed and reinstalled to perform this work.
Rocky Mountain Driveline has the machinery and expertise onsite to resurface flywheels. A resurface will help to restore like-new operation to your clutch assembly.