I'm working on a 96 F150, 4.9, C6 for a neighbor. At wit's end. Between him, his brother, nephew, repair shops, myself and whoever they've been able to get to try fixing it, the truck has had at least 3 flywheels, 2 block plates, and no exageration at least 25 starters through the past several years. I personally have put 8 or more on it. I changed flywheels twice and block plates once. I gave up at one point and they took it to a shop that told them I was using mexican flex plates from O'Reilly's, so they went to a salvage yard and got a Ford plate, no difference. Sometimes it works a little while then chews the bendix teeth up or flex plate teeth or both. At one point I filed the mounting holes out and shimmed the starter closer to the block but it only helped a month or so. I did that by cutting tubing in half and putting beside the bolts. Is it possible the holes in the transmission are indexed wrong ?? Thanks.

 

Can you better describe what is happening that is requiring all the replacements?

 

When starter is replaced, it either immediately or within a few days starts zinging like a bad bendix. upon pulling the starter, the teeth are either chewed at the leading edge or as is the case now ground off where it wasn't engaging deep enough and started over riding. they appear to have been going back far enough, just not down into the flex plate deep enough and any kickback would cause the teeth to override each other and grind down the height of the teeth on the flex plate starter ring and also the teeth on the bendix. It acts like the flex plate is about a quarter inch too small in circumpherence . Although as I posted, this is at least three flex plates that have been used from several sources. The one in it now has been damaged by the present owner's attempt at shimming the starter with washers, which WE all know only pulled the starter away from the transmission and at an uneven angle at that. Then to make matters worse he had lost the correct bolts, stripped the threads and couldn't keep it tight, further damaging the teeth on starter ring. I know about the different starters for auto and standard shift but it couldn't have been the wrong starter 25 or more times. When I replaced the flex plate, block plate and starter all at the same time, I know I had matching parts, even though they were from O'Reilly's. At that point it had the correct bolts etc. but still within weeks experienced failure. I know this is a long reply, but trying to get as many facts out there as I can. ANY help is great. Even though I said a while back I would not touch it again, the challenge to be the one to finally solve this problem is too great. I'm almost convinced that the boltholes in the trans case are too far outboard to let the teeth mesh properly. Any thoughts??

 

I looked at websites of the auto parts stores and found something that may have some bearing, but it's only listed on Motorcraft starters. There is a production split of before and after 7/15/96. This showed up on Rock Auto and O'reillys. The description lists the earlier starters with 10 teeth and later with 12 teeth. This would most likely affect the diameter of the starter gear by a small amount. May be worth looking into.

 

GREAT!! That's the BEST lead I've had since I first started fooling with this pig 3 or 4 years ago. Have almost lost friends because of it. Genius... I'll definitely be checking further,since it falls into that very year break. Thanks again and I'll post the results.

 

I am so sorry!!! I mistakenly said it was a 96 when in fact it is a 87. Built in 11/87. Frustration mounts. Thank you for the help and I'm very sorry for the mistake. Any further help??

 

I was wondering about a C6 in that late of truck. I had an 86 with the 4.9 and a 4 speed and it kept busting the nose of the starter. Turned out to be a couple of chipped teeth on the flywheel that would cause the starter to go tooth to tooth and the leverage would bust the nose off. Changed all out like you did and no further problems.
The things I would check at this point are to make sure you're getting the right flexplate. There are different ones for C6 and AOD. According to part sites, your starter drive should have 9 teeth. Other things might be a shim between crankshaft and flexplate for whatever reason. Something up where the converter bolts to the flexplate causing it to warp a little. Are the trans and engine square to each other? Is the engine the original one? Maybe there is a difference that requires you to use a different starter. Are you sure all the bolts were torqued in proper sequence to prevent warping. I'm a little over cautious and prefer to do mine in stages like cylinder head bolts to keep it straight. A little more time consuming, but I haven't had to go back into one to redo it. Another possibility that happened to a friend of mine is that the place that made the flywheel mounted the ring gear at the wrong depth. Not to easy to do with a flexplate, but you never know what could happen when factory workers are looking forward to a three day weekend and it's late Friday.
That's all I got for now. Maybe others might chime in with more suggestions or experiences. It's a little difficult without seeing everything in person.

 

Did you ever figure this out? I am having the same problem with my 79 bronco 351m with T18 tranny and nobody can figure it out.