Starter wont engauge flexplate

Im trying to start up the F100 for the first time. When i turn the key the starter makes a funny noise for a second and then just free spins not grabbing the teeth on the flexplate. All the teeth on the flexplate are still there. I even turned the motor a bit by hand to get a different spot on the ring gear...still a no go.

I took the starter out and hooked it right to the battery and it spun and the gear popped to the end of the shaft like it is suposed to.

Could the starter be messed up in a way that when out of the vehicle it acts like its good, but when its mounted its not?

YES check the gear I have seen them slip when in engaged look fine floor testing it but wouldn't crank my gear was busted it had a hair line crack in it

IF ... the enguagement is fine then the sprag inside the bendix is probably slipping.

Not a common problem but, it does happen.

Is there some "wiggle room" with the starter loosely bolted up? Maybe it needs to move towards the frame rail a tiny bit?

I got it. Now I got a fuel leak at the carb to fix.

Are you sure you have a starter for a Auto. If its for a stick it won't engage far enough to catch the flywheel.

Was that your problem Rick?

On the one my brother gave me it was. I might take it tomorrow and get the Face turned down so it will set back far enough to catch the FW.