Symptoms of a Bad Flex Plate

The flex plate 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 flex plate is in good operating condition at all times.

The flex plate is a metal disk that mounts the torque converter in an automatic transmission to the rear of the engine’s crankshaft. The flex plate has a ring gear around its circumference, which mates with the starter motor when you start your car. As its name suggests, the flex plate’s thinness and light weight allows it to “flex” and absorb any irregularities in the engine’s power output, as well as minor misalignments between engine and transmission. In general, the flex plate and the torque convertor work together to smooth out the flow of power from your engine to your transmission.

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

Symptoms of a bad flex plate

A problem with your flex plate can be very dangerous. Because your flex plate transmits the power from your engine to your transmission, your ability to control your vehicle’s power can be affected. A bad flex plate 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 flex plate. Here are some of the warning signs of a bad flex plate:

• Clunking, grinding, chirping, or rattling noises from rear of engine when engine is idling
• Knocking noise when engine is shifted into drive or reverse
• Heavy vibrations felt through the driver’s seat when driving at normal speeds
• Rough-running engine
• Loss of power at higher speeds
• Poor fuel economy
• Starter makes whining sound during starting
• Starter bogs down, has difficulty turning during starting

Very often, a bad flex plate is an indicator of another powertrain problem. Most commonly, the transmission may be malfunctioning.

Repairing a bad flex plate

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

Your mechanic will first inspect the condition of the flex plate after removing a cover provided for that purpose. After confirming the need to replace the flex plate, the transmission will be removed from the vehicle. Next comes removal of the bad flex plate, replacement with a new one, and then reinstallation of the transmission into your vehicle. Your mechanic will also check your transmission for any other indicated problems, and then make sure that the engine and transmission are properly aligned before finishing the repair process.

Don’t try to repair a bad flex plate yourself

Unless you have had extensive experience in working with automatic transmissions, leave this to the professionals! Your flex plate must be installed precisely, have its bolts torqued down to the correct settings and in the right sequence, and also be aligned correctly between engine and transmission.

If the repair is not done properly, you will be replacing your flex plate again before long, with the potential for some serious transmission damage. Your mechanic has the proper tools and equipment to replace your flex plate safely and efficiently.