Starter spin but no crank

Sometimes there may be several teeth in "succession" that are bad on the flywheel--but not likely for ALL to be bad. More likely for a bendix not engaging starter (driving gear) into flywheel teeth (driven gear) than for ALL teeth to be bad. How did you check your starter? I've seen them spin normally with voltage applied lying on a test bench; but, if the bendix is not engaging, it cannot turn the flywheel when bolted in place on the engine. Your "grinding" noise, sounds, however, like several bad teeth on the f'wheel. But, check for proper bendix operation(simple problem) before assuming the f'wheel is bad(major problem). Luck!

Sounds to me like the overrunning clutch (aka "Bendix") in the starter drive is not holding. The pinion will spin fine on the bench, and will engage the flywheel. But if the O/R clutch is chattering, the pinion will just sit there and vibrate, sounding a lot like gnashing gears.

Sounds like the "clutch"-like mechanism in the starter's pinon may be worn out.

On one of my cars the starter would spin without cranking the engine then there would be a clunk. The next turn of the starter would crank the engine. I found that the front part of the housing was cracked as well. I replaced the front part of the housing from a junkyard starter motor and bought a new pinon gear assembly. It's been fine in all the years since.

Approximately 11/16/03 21:32, abc uttered for posterity:

Not likely that all of them did, but it is possible that a small section of the flywheel has had the teeth busted off...happened to me oncet.

Could also just be a defective starter where the pinion gear isn't being forced out into contact with the flywheel hard enough.

I like Steve's answer better than mine. Conclusion: replace the "bendix", or entire starter. sdlomi