After only 7500 miles on a 914 conversion to fresh six and 901 gearbox, the new flywheel ring gear was trash. The drive gear on the Bosch starter showed no damage or unusual wear despite catastrophic destruction of the ring gear. The starter was returned to the auto-electric shop where it was serviced prior to installation, was inspected and no problems found but replaced the drive gear. We also verified it was the correct starter for the application. I did a "hardness" test on the flywheel teeth with a file and didn't feel much different than mild steel but it sprayed sparks when hit with a grinder. Inconclusive.

Logically the starter drive gear should fail before the ring gear (small gear/high revs vs big gear/low revs) at a ratio of about 14 to 1 tooth contacts per revolution. So----why did it fail?

Heck if I know.

I counted 36 listings for flywheels on ebay that fit 65-69 911 & 70-71 914-6. The vast majority are from one of two German OEM manufacturers, WD Express and Sebro. The market is flooded with WD Express. The Sebro could be as much as $100 more than the lowest WD Express if you consider shipping (some not free). Anyone have any experience or knowledge of either of these OEM flywheels?

How about plan B, farm it out and replace ring gear only (weld on?)

Hate to be the bearer of bad news, but the flywheel is trash and un-repairable.

It seems like this is seen much more often than in the past. I wish there was a conclusive answer.

Thanks for the reply. I got the same feeling based on other comments on the forum and the glut of flywheels selling on ebay.

This is usually an engagement issue where the starter part does not extend far enough to fully engage the teeth on the ring-gear.

Induction hardening is the correct way to treat flywheel teeth,appears this hasn't been done or correctly,yes I do agree that poor starter engagement could do this but not over 7500 miles.
There is no way a file will touch the tip of the teeth if they are heat treated properly.
Are the suppliers of these flywheels taking them back for a refund or replacement when this happens ??

There is a way I can repair it, but it will likely cost more than a new flywheel.

That's because you are a wizard, and everyone knows wizards aren't cheap

discussed before - many times - google is your best friend

https://www.google.com/search?q=911+flywhee...-8&oe=utf-8

https://www.google.com/search?q=911ring+gea...amp;newwindow=1

i posted cause & solution both here & on Pelican - - simple answer - RIMCO can put a new ring gear on it & save you about $300

http://forums.pelicanparts.com/porsche-911...ear-repair.html

http://www.914world.com/bbs2/index.php?sho...75173&st=40


what starter are you using?

- Bosch 1.5 starters had a thin nose bushing that cracked - the gear was then a bit out of align - the usual cause of this problem - once i got rid of that Bosch starter, never had another problem -

there are also a couple threads on that

also see the threads suggesting need for a shim with some aftermarket starters

fwiw - am currently running an IMI HiTorq

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