F 150 Starter Problems

I have replaced the starter and the soleniod switch and when I try to start my 1986 6cyl. it sounds like the flywheel and starter are grindig,put new flywheel on several months ago,the battery appears to be fine but the sound it make when starting is terrible!Any suggestions?

does the new flywheel have the same number of teeth as the old one?

Yes,it has the same number of teeth,I was told that maybe I needed to shim the starter out,but i'm leary of that.

I think there is only one shim you can get and it is thick. but if the teeth are the same you will have to try a shim or new starter

I tried a shim,same problem,my starter is only a month old and is the 3 one i've put on in 6 months,I keep swapping them out hoping to fix the problem,one thing I failed to mention is that after I start it and the engine warms a little,it starts fine,but it sounds terrible on cold starts!!

are the bolts that hold the starter on factory bolts?

They are the bolts that were on the factory ford starter when I bought the truck a few years ago,I'm beginning to think it is a timing problem because I can see the radiator fan try to turn backwards when my starter is going crazy,like the engine is combusting early,those old hand crank cars would kick backwards and break peoples arms,I am going to check timing and I hope that is the problem because it is driving me crazy!