These forum discussions might give you some more info:
starter starter2The engine has to be separated from the trans to replace the flywheel gear.
flywheel is a picture of the end of the engine, the big gear is the ring gear/flywheel. It could be the starter or its alignment too. If your car is a stick shift you could try to bump start (it won't), that would move the flywheel from its current bad spot, and try the starter again. If it works, you might need flywheel. Remove starter and take a look.