Signs of a Bad Flywheel

The flywheel is a key component of your car’s powertrain, which includes the engine, the transmission, and the other related parts that get the power to the ground. The powertrain is very important to your car’s acceleration, shifting, and cruising, so it is essential that your flywheel is in good operating condition at all times.

The flywheel is a large, heavy metal disk that mounts to the rear of an engine's crankshaft. Its purpose is to store rotational energy, as well as to smooth out the fluctuating forces of the individually firing cylinders. The flywheel has a ring gear around its circumference, which mates with the starter motor when you start your car. The flywheel and the clutch work together to provide a smooth flow of power from your engine to your transmission.

If your car has a manual transmission, it most likely has a flywheel. If your car has an automatic transmission, it does not have a flywheel. In manual transmission vehicles, the flywheel and the clutch perform a similar function to that of the flex plate and the torque convertor in an automatic. Despite their similar functionality, a flywheel and a flex plate are two completely different types of components, and they are not interchangeable.

Symptoms of a bad flywheel

A problem with your flywheel can be very dangerous. Because your flywheel transmits the power from your engine to your transmission, your ability to control your vehicle’s power can be affected. A bad flywheel could potentially cause a loss of power to the wheels and result in an accident. Many factors can cause wear to and deterioration of your flywheel. Here are some of the warning signs of a bad flywheel:

• Abnormal noise when starter motor is engaged
• Rattling noise when depressing or releasing clutch
• The clutch "grabs" when engaging
• Car slips out of gear, going into neutral or another gear
• Shaking or vibration felt through the clutch pedal or floor of the vehicle
• Burning smell from clutch
• Clutch chatters when engaged
• Clutch drags, will not release completely
• Inability to change gears
• Pulsation felt through the brake pedal

Repairing a bad flywheel

A bad flywheel usually has failed due to either damage or wear and tear, so replacement with a new flywheel is the standard solution. Because the flywheel is an integral part of your car’s powertrain, and replacing it involves removing the transmission to access the flywheel’s location on the engine, a significant amount of labor will be involved.

After confirming the need to replace the flywheel, your mechanic will remove the transmission from the vehicle. Next comes removal of the bad flywheel, replacement with a new one, and then reinstallation of the transmission into your vehicle. Your mechanic will also check your starter gear, clutch, and transmission for any other indicated problems before reassembling and testing your powertrain.

Don’t try to repair a bad flywheel yourself

Unless you have had extensive experience in working with engines and manual transmissions, leave this to the professionals! Your flywheel must be installed precisely in the correct position, with its bolts torqued down to the correct settings and in the right sequence.

If the repair is not done properly, you will have the potential for some serious transmission or engine damage. Your mechanic has the proper tools and equipment to replace your flywheel safely and efficiently.