915 5 speed serious clutch chatter

[911pcars]

Originally Posted by javadog

The measurement is the runout on the perimeter of the flywheel. I don't know that Porsche intended it to be measure while installed on the engine.

JR

How else would one measure runout if not mounted and rotated in an equivalent fashion? To confirm nothing is going on with the crank-to-flywheel mounting surface, measure that too - although finding an equivalent disk to replicate a mounted flywheel might be a challenge (e.g. new flywheel). However, even a used flywheel should be true if runout is measured on a non-friction, machined surface.

An automotive machine shop should have all the facilities to confirm a flywheel is okay/rebuildable. Even new parts could have manufacturing defects.

Sherwood

[javadog]

Originally Posted by 911pcars

How else would one measure runout if not mounted and rotated in an equivalent fashion?

It can be mounted and rotated on things other than a 911 crank...

Imagine you are refinishing it. You have it mounted on a lathe, or other machine...

Probably Porsche's intention... make sure after maching that it is within specs.

JR

[john walker's workshop]

one must take into account the crankshaft end play when measuring runout when the flywheel is attached to the crank.

[heiltrading]

Machine shop found about .006 in run out and removing that material. Im still way over the .335 thickness spec. The machinist seems confident I will have no issues....Thoughts?

[heiltrading]

shop used a diamond cut to remove material....

[911pcars]

Originally Posted by heiltrading

Machine shop found about .006 in run out and removing that material. Im still way over the .335 thickness spec. The machinist seems confident I will have no issues....Thoughts?

Sounds good. Is that the latest pressure plate in the photo? If so, that was paired with the flywheel with excess runout. You may now want to machine the pertinent pressure place surfaces to remove any localized and heat-hardened areas on the plate caused by unevenly applied pressure (depends on miles and usage with the plate). Ask your machine shop about this.

They may not have the correct tooling to D&A and resurface the PP, but they could offer their expertise and maybe a referral to a clutch rebuilder.

Sherwood

[javadog]

Originally Posted by heiltrading

....Thoughts?

I give you 50:50 odds.

JR

[john walker's workshop]

Originally Posted by heiltrading

shop used a diamond cut to remove material....

a diamond stone can retain a sharp edge so the outer edge where the pressure plate needs to sit flat on is not bevelled.

[heiltrading]

Pressure plate only had 2k miles on it and I have a new friction disk ready to install today. 50/50 odds

[Peter Bull]

I had a similar problem om my car. The chatter was really bad unless I released the clutch pedal carefully, and with a limited amount of revs. Quick starts were impossible.

It turned out that the source of the problem was poorly adjusted clutch wire and clutch pedal. After carefully following the procedure described in Wayne Dempsey's book, it worked like a charm. Now I can take off with spinning wheels without any risk of the clutch shaking itself, the transmission and the engine to pieces.

I believe the procedure is described in both the Haynes and the Bentley manuals, too. I had them both in my garage, but didn't know just how important it was to follow the correct procedure. Now I know.

/Peter

[SCadaddle]

Originally Posted by heiltrading

Assuming your bell housing had a gap on the bottom? This should be obvious when under the car?

Yes! Once on the lift I asked my friend the 911 Guru (who wasn't a party to the problem) if the gap at the side by the starter looked correct to him....it was a WTF! moment. Luckily we were able to use a pair of thin nuts to double nut the stud and remove it from the engine thus freeing the offending washer.

[heiltrading]

Problem solved!!! The end result due to resurfaced flywheel $32.00, new friction disk $139, and new throw out bearing $130. The clutch releases with absolutely not chatter and now the transmission is much easier to put in first and reverse, probably due to the prior poorly adjusted clutch cable.

Ready for spring