Why always having to replace my starter

There is a Ford 351 Windsor and then there is a Ford 351 Cleveland and they are close but not identical. As Tom asked, what failed? Are the teeth on the starter gear not fulling with the flywheel and "rounding off" or has the starter motor failed? Wassup?

Back in my younger days I had a 68 roadrunner with a 383 I purchased used. The owner gave it up because he kept having to change starters. I began having the same problem. Found a roadrunner GuRu who immediately found the problem. Seems there was a heatshield over the starter because the exhaust was close. Someone removed the shield and failed to replace it. Installed a new shield and no problems. If there is a shop in your area that rebuilds starters, take it there and have them determine what failed. That may lead you in the correct direction. NOTE: I do not purchase parts from Autozone any longer. To many bad alternators, starters, powersteering pumps, etc. bad out of the box.

I had someone tell me it it possible that the fly wheel may be backwards. It is eating the middle of the teeth on the starter gear. And when it stops working it makes a really loud screaming noise.

shim your starter and make sure oil isn't leaking all over it

The screeching sound will occur if the starter gear is not fully engaging in the teeth of the fly wheel. On older vehicle this was caused by a weak bendix spring in the starter not fully entending the gear at the the fly wheel.

wrong starter

I'm have the same problem and I put all New parts on it

A lot of rebuilt starters are total crap. Look for good ones that have been properly rebuilt, most just repair one thing and the rest of it is used.

I feel your pain, i have put 11 starters in my 1988 f250 351w in a year and 3 months have also replaced flex plate three times, i have driven fords most of my life but im now considering a mule or moped.