Pete L

Greg

Confirming, no risk to turn a 32V backwards provided belt tension is correct w/ stock tensioner? I just measured on a 9201 and its 5.2

AM I on target with assessment above?

Pete L

I removed the clutch today.

Below is a photo of the flywheel when last apart. Note ring tooth gap is 7 (seven) teeth to the right of the bolt hole in the flywheel.



Here is the flywheel today - the ring tooth gap is 2 (two) teeth to right of the bolt hole in the flywheel.



Thus, the ring has slipped at least 9 teeth or 3.3 degrees X 9 or circa 30 degrees. That explains the initial timing of 15 degrees ATDC instead of 10 degrees BTDC (25 degrees difference)

The ring appears to have slipped towards the rear of the car when comparing to the old photos today as well

I'll post photos of the clutch etc, like to get opinion if disks need to be replaced.

Finally, this problem is figured out,

Imo000

Wow, I'm surprised it ran at all.

M. Requin

There appear to be signs of metal to metal contact on the lower right quarter (referring to the photo layout) of the ring gear, or is that just some effect of the light?

Pete L

No metal, just some smeared penetration oil that was used on the dowel pins.

Also, my assessment is the rig moved 7 teeth or 7 x 3.3 degrees or 24 degrees. This corresponds to exactly what i read on the damper for the timing at idle

M. Requin

Ah, thanks for the clarification, and also for the info about timing at idle which should help anyone looking for a possible simple way of detecting the possibility of this problem.

SwayBar

Nice job diagnosing!

V2Rocket

any reason not to tack-weld the ring to the FW in a few spots?

Pete L

Probably just going to get a new flywheel to save time and agravation ad getting ring aligned and trips to machine shop.

Mrmerlin

I would run a bead around the joint with some green loctite that will hold it in place as well as drill a hole and pin it

Pete L

Looks like I need either a new flywheel or get the old one repaired. Old one came off this evening after I got a triple square 12mm to remove the bolts. Part #928 102 078 01. Looks like this part is rebuilt from Porsche as dealers want a core charge. Maybe I will send this flywheel to Carl at 928 Motorsports as he told me he has a jig to get the alignment correct.

Below are photos of the disks? Any opinions on if they need replaced? Thickness (overall) is as shown on the caliper








How can I best check throw out bearing and determine if it is still usable (has about 50k miles) Seems to rotate w/o binding or noise

jcorenman

Thickness doesn't mean much, because of the Marcels (wavy-springs between the two surfaces). The rivets look OK however, there is plenty of meat left and the disks don't look toasted.

PET shows 928-102-078-X for that flywheel, "X" being rebuilt with core required. MSRP is $623. A better deal would be a used one from 928 Int'l for $400, or a much better deal would be to wait a few weeks for the half-price sale.

And of course if Carl has a jig and can reassemble it properly and tack-weld it, then that is almost certainly the best deal. But I would first tap the ring off and check it carefully for any cracks, it is extraordinary that it slipped and that has to mean something. If it is just a tolerance issue then tack-welding will fix it permanently.

Given the miles and the shape of the discs, the TO bearing is probably fine. I wouldn't change it unless you want to refresh the whole clutch, and that's a slippery slope cost-wise. These clutches aren't that hard to get to, WYAIT isn't a big deal.

Mrmerlin

if you can see the TOB bearing shield,
then you can drill a small hole in the shield with a new drill,
then fit a hypo needle thats screwed onto a zerk fitting,
then use the grease gun to inject grease into the bearing ,
then seal the hold with a dab of silicone, the fresh grease will prolong the life of the bearing.
NOTE the bearing spins at engine speed all the time.

Pete L

I will replace the pilot bearing (have a puller that works well , no hype needed needed) and possibly the TO bearing using the press in replacement.

Will send flywheel to Greg Brown at precision to re index + weld the darn ring, exchanged several messages with him today. No used flywheels at 928 International or with Rodger.

Hopefully I'll get the beast back on the road and enjoy it a bit before I sell it

I may post in order photos of the remove / reinstall process of the dual disk clutch, have lots of photos

Pete L

Took my flywheel to Precision Motorwerks on Wednesday. First time there, 928 nirvana! Met Greg Brown.

Greg had a 86 5-speed flywheel, below is a photo of my flywheel with slipped timing gear ring vs a correct 86 flywheel

The ring did and has moved around 25 degrees (7 teeth at 3.3 degrees per tooth). I presume this will correct the drive ability, low power, low vacuum etc

Thank you Greg Brown, Mrmerlin, Carl Fausett, Strosek and John Speake for your input on solving the mystery.

Greg will rework my flywheel + TIG weld in place. I will post photos of reassembly to help others with dual plate clutch on the R and R process