Starter grinding

If its got a "stall" (convertor) then it has no flywheel. the ring gear is on the convertor. If you pull your starter, the gear should snap out pretty sharply when you apply 12V. your ring gear may be worn in the 4 "spots" where it usually lands. Also make sure your starter is seated in the snout hole and bolted tight. Hitting with a hammer is a sign of a bad magnetic solenoid actuator on the starter itself. It can be dissected and seen as the top "can" on top of the starter motor.