Weissach

My car has started shudering/judering when taking off from a stand still(5-speed). The motor mounts are new, so I think it might be the clutch or flywheel?? Is there an easy way to check? It feels like it's a warped flywheel(I've experienced the same symptoms on a 911 and it was a warped flywheel) but this is the dual disc clutch, so I'm not so sure.

If it is a warped flywheel, whould it be possible to remove it with out having to also take of the clutch and having to re-adjust it?? Any help would be greatly appreciated.

Jim_H

Doubt it's a warped flywheel. Sounds like it's time to replace the throw out bearing.

Garth S

Oil inleakage from rear main seals or even oil collection in the 'Vee' (from all sorts of leaks) can migrate to the clutch area to cause these sorts of problems; The T/O bearing Jim noted, the release lever pivot and bushing, guide tube, discs worn or splines binding on the intermediate shaft, pilot bearing, etc can all contribute.
How many miles on the clutch? - The pivot can be checked under the air box, and drop the botton bell housing cover to see much of the rest. The flywheel and intermediate plate are pretty sturdy items, and at worse may need a 'buff' with emery cloth if the surface is marred.

hupp

In my opinion the shuddering is more than likely caused by the following:

- Hot spots/warped flywheel
- Weak pressure plate springs
- Worn discs

Styln928

Ernestsw & I both had the same problem. It turned out to be our pilot bearings. Both had discinergrated which caused the problem your discribing. I sent mine to the shop & Ernest did his. Hopefully he will chime in and help you with this.

HTH

ErnestSw

Actually, I never had a problem with shuddering, My symptoms were an intermittant metalic clunk with engagement and disengagement and a rotational noise on disengagement. Shuddering in an otherwise properly functioning clutch is usually caused by a problem in the engagement process. Something is preventing complete contact of both mating surfaces all at one time.
Replacing your motor mounts may have suddenly changed the geometry of your system causing the problem.

JKelly

I have some occasional "shuddering" also, mainly when starting out in reverse. I replaced my motor mounts earlier this year (with anchor mounts) and a few days after that the throwout bearing starting chirping (hearing crickets). The clutch seemed to work better after the motor mount change, but it still shudders. I have often wondered what effect(s) sagging motor mounts have on the clutch . I have dropped the lower bell housing and greased the TO bearing for a temporary chirping fix, but am now ready to replace both TO and pilot bearings and anything else that looks worn. I noticed that the clutch fork bushing was shot, which sometimes causes a rattling noise. Since I put an Ott x-pipe on, the clutch is simple to get to so I think I'll start replacing the obvious problems first (after a good clutch bleed) and see what problems are solved before I start replacing plates. So, all in all, the symptoms I have are occasional shuddering, occasional rattling, and intermitant chirping. I know that the throw out bearing is bad (chirping) and the clutch fork bushing is bad (rattling). The clutch has 73k miles on it.

Jim bailey - 928 International

The clutch fork bushing (white plastic socket) is very important for maintaining the correct pull and geometry on the release bearing. When the bushing breaks falls out the top of the clutch release arm it then rides too far forward and when you depress the clutch pedal and the slave cylinder pushes the bottom of the clutch arm toward the rear you are not pulling the release bearing evenly. The uneven pressure on the spring fingers somewhat warps the pressure plate and upon release one side hits the friction disc harder and it skips....judders especially if you are slipping the clutch a bit more than needed.

heinrich

That's why when you have a technical question, you should ask someone who knows. Stated a different way, WWJBD Mr Bailey

Weissach

The clutch is maybe about four years old(clutch has about 18k miles). Well since I'm going to do this myself, I need to know a few things. 1. How hard is it to replace to clutch and flywheel?(harder than motor mounts?). Is possible to change the the flywheel without taking apart the clutch? Should I put in a new clutch even though the old one doesn't have alot of miles? Anything else I should know before I attack this.

Jim bailey - 928 International

the clutch assembly is bolted to the flywheel by 9 bolts around the perimeter of the pressure plate. So to see the flywheel you first remove the clutch assembly . It is not common for the flywheel to warp on a 928 BUT it has happened.

Garth S

At 18K, there should be a lot of life left in the clutch: anyway, dropping the clutch IMHO, is a lot easier than doing the motor mounts - there are some aspects, like getting the dowel pins just right, pilot bearing, etc.
However, before going 'gung - ho' on removal, remove the air box and check out the release arm pivot/bushing as previously mentioned. If the plastic cup in the arm is kaput, do a search on it: I recall that it may have been replaced from above after backing off the slave cylinder - maybe that is just wishful thinking.