Fly wheel questions

[The Jug]

Hello all ! happy New Year ! I have 1991 case 590 back hoe loader . I’ve been haveing starter problem . First one I bought from let’s say less than reliable parts source . Gave it a try still skips ( grinds ) So then went to reliable parts source brought the original case starter and he sold me after market . Still skips (grinds ) . I have one new battery and one ok still test good not full but ok . Took a look at starter ringing gear (fly wheel ) through the starter hole corners somewhat rounded but all in all teeth look ok . Not sure watt way to go with this . Any thoughts would help .

[Hurlbutt]

I don't know the machine. But, I'd check the manual to see if there were shims used for adjusting the tooth mesh of the starter drive with the ring gear. If it were too tight the pinion wouldn't be able to mesh with the ring gear and just grind on the face of the of the teeth. With Chevys you could some weird beseeching sounds if too little shimming was used.