My 96 z28 gets a really bad grinding noise when starting.  It only does it sometimes.  Mainly when it is cold.  I havent got into checking the starter yet, but i think it could be a combination between that and the ring gear of the flywheel.  It still turns over, but sometimes it takes a few tries.  Anyone think this could be the problem?  If so, do you know how big of a job the flywheel is?  Thanks.