I think I know the answer, but need a second opinion.

I have an 81 F150, 5.0 engine with an A/T. It has started eating starters. They will sound okay for a few days then start getting really loud and eventually hitting a bad spot where they just spin.

Today after it did this I pulled the starter, looked at the flexplate and couldn't see anything obvious. I marked the spot, rotated the flexplate to the next bolt, and reinstalled the starter. It started (loud) a few times, then freewheeled again. Pulled the starter again and it had stopped at the exact spot I had marked before.

Put my brand new backup starter in, following the same procedure as above, and it did the same thing.

Seems to me it's a bad spot on the flexplate.

If no teeth are missing, what else should I look for?

 

I'm assuming that you are looking at the Flywheel. Sounds like a C6 transmission. Where are you procuring the starters from ?

 

Flex plates are used with auto tranys.
Fly wheels used with stick tranys.


Have you checked/measured the throw of the gear on the starter from the starter face then from the starter mount to the flex plate to see if the gears mesh fully.


Now I have seen it posted 1 starter for auto and 1 for stick but don't know if that is true for you?
Could be the flex plate is not true / warped from the stand point of the starter face. Or could be out of round and why it does what it does but either way I would think the teeth on the flex would be eaten up?


Dial indicator on the starter mount to see if the flex is warped front to back. Don't know how you could check out of round because of the teeth?


I think it is GM you have to use "starter" bolts because of the shoulders they have is Ford the same way? I am newish to Ford so don't know.
Dave ----

 

Has this ever happened prior to this ? I still think that the initial starter failed....and the replacements (AP rebuilt's) were sub-standard.
A Flexplate/Flywheel doesn't "just fail" out of the blue unless it is very high mileage or subjected to severe service or subjected to starter issues. Warpage ? Rare. I'd look to a Motorcraft starter.

 

A flexplate has been known to develop cracks in it.

 

But Ford never used the term flexplate, all M/T's and A/T are called flywheels.

 

Ford did not use any "shims" for mounting starters, and no special shoulder bolts either.
I have always just "bolted" the new on, and off we go... never had a problem.