A flex plate is the flat piece of metal that connects the engine to the transmission's torque convert. Most have teeth around the edge for the starter to engage into when starting your car.
A automatic has a flex plate and a tork converter.. A manual trans has flex plate and fly wheel...
remove engine or transmission replace flex plate (flywheel).
To my knowledge the only small block flex plate that doesn't interchange is the small block 400.
your spacer plate and starter should be the same the flex plate and converter will need to be replaced
the purpose of the flex plate is the same as a flywheel. when the starter is engaged, it spins the flex plate, thus hopefully starting the engine.
You Have to pull the transmission or at least pull it back so you can reach the bolts holding the flex plate to the crank.
If it really IS the flex plate, that's a lot cheaper than other problems that could cause a bad knock. The flex plate is a steel plate that bolts to the rear of the engine and has gear teeth around it. The starter engages with the teeth to start the engine. The torque converter also bolts to the flex plate. All power produced by the engine that is used to move the vehicle goes through the flex plate. Flex plates get old and sometimes crack. When that happens you want to get the old flex plate out of there as soon as you can before it breaks completely and destroys the torque converter. A flex plate is relatively cheap, compared to a complete engine rebuild or replacing the torque converter. To replace the flex plate, simply pull the engine (or transmission, whichever is easiest), unbolt the flex plate from the crankshaft, bolt up a replacement and put the transmission (or engine) back. Of course, there is more involved than that, but it's not as bad as some repairs.
You have to pull the engine or transmission. The Flex plate is at the back of the engine on an automatic transmission. 6-8 bolts hold the plate to the engine, and four bolts hold the plate to the tranny.
The flex plate connects to the crankshaft and bolts to the torque converter. The flex plate also has a ring gear that meshes with the starter. If the flex plate is in good condition it can be re-used. Check the gear to make sure that none of the teeth are worn. If all teeth are still in good shape and there are no cracks in the flex plate it can be reused. very commonly found in older ford f250
Flex plate
Flywheel
The transmission has to be dropped first. then the torque convert/clutch needs to be removed to gain access to the flex plate, which can then be replaced.