Brett Jenkins

My clutch slips during a moderate launch and if I have it in 5th at low speeds, so I think it's time for some clutch work. I have 81k miles.

What's the minimum suggested parts to be replaced. Is it necessary to replace the pressure plate, or can just the disc and ancillary parts be replaced? I noticed on several vendor sites that they mentioned that the guide tube needs updated during the 1st replacement. Is this necessary as well? What other seals/bearings/bolts/etc should be replaced?

I guess I'm looking for an economical fix, but I want to do it right. I'll be doing it myself. So, I'm looking for a list of everything that I will HAVE to replace and also other things that I SHOULD replace. A mention of any special tools would be nice as well. Thanks.

Anybody want to have a clutch party?

AO

The minimum would be the friction plate and clutch arm bushing and you'd reuse the thow out bearing and pilot bearing. But a more realistic minimum is TO Bearing, Pilot Bearing, clutch arm bushing, friction plate.

The TO bearing can be a pain to replace. You can build your own "press" but if you have access to one, that'll make like much easier. You may also need a pilot bearing puller - search the archives.

If you re-use the bearings, you can doe it with relatively few tools. I used a jack to raise and lower the clutch pack and to avoid letting it drop on my face. Worked pretty good.

I hope I didn't miss anything - I've only replace the clutch once - but it took me 5 times!

cfc928gt

I'd say minimum is disk, clutch arm bushing and pilot bearing. The bushing and bearing are inexpensive and both are prone to failure. If you're replacing the throw out bearing I believe you need a new release arm and guide tube too since the original throw out bearing for an '88 is no longer available.

pmotts

Yep. Do a search on grenaded pilot bearing and your decision will be made easy.

Brett Jenkins

What would be the deciding factors of whether I should/shouldn't replace the TO bearing, other than the obvious WYAIT reasoning? What are the symptoms of the TO bearing going bad and what are the repercussions of it going bad if not replaced. Would it just be another R&R job if it does go bad?

If I'm just doing the disk, clutch arm bushing, and bearing, then I don't need to install an updated guide tube or release arm?

What disk? Sachs? Porsche? or ??

Brett Jenkins

Decision on whether to do the pilot bearing or all of it?

I'll definitely do the pilot bearing, but was hoping to avoid clutch arm, guide tube, pressure plate, etc. unless they are necessary replacements.

cfc928gt

Are you getting any noise at all from the throw out bearing? I use the drive up window at my bank. Nice brick wall two feet away from the car. Put it in neutral and push the clutch in and out and listen for any strange noises. Since you do your own work it doesn't cost anything other than time and aggrevation to go back in and replace the throw out bearing if it starts failing.

heinrich

did you inspect it first? May not need a clutch job.

Brett Jenkins

Absolutely no noise when I push the clutch in and out. The only clutch related noise I notice is a slight "rattle" at moderate RPM's which will go away if I every lightly push the pedal. Almost seems like the pedal itself is rattling or maybe the arm?

The only clutch problems I am having is a bit of slipping during a moderate to spirited launch, which will carry over to 2nd gear if I over rev and it will grind a bit sometimes when I downshift from 4th to 3rd, depending upon RPM's. If I don't take off hard, the clutch works beautifully, but I wonder how much power/efficiency/fuel mileage I'm actually losing because of a slipping disk.

Jim bailey - 928 International

When a clutch slips it is because the disc is too thin or the pressure plate springs have LOST their spring and the clamping force is too little or as in this case someone abuses the clutch by slipping it on a drag race start . When it is slipping it overheats the friction material "glazes" and at the same time the heat burns hot spots blue marks on the flywheel and on the pressure plate surface since the slipping is on BOTH sides of the friction disc. So the minimum would be a friction disc which is thicker and would POSSIBLY compensate somewhat for a weak pressure plate. If there are burn blue spots on the flywheel it "should" be surfaced ,you cannot surface the pressure plate since that reduces the dimension and the spring pressure , blue spots can cause shudder or judder as you try to engage the clutch.

worf928

What JimB said.

If the bushing on the ballcup for the release arm lever is shot (which it probably is) you will get a noise like you describe.

WSM has a procedure for checking friction disc wear through the inspection hole.

My '91 slips too. It has 1/2 of the disc left. After 15 years a pressure plate gets tired.

Brett Jenkins

Will that bushing being worn cause more than just the noise?

I'll inspect the disc tonight. Is there some sort of built-in thickness gauge or?? to determine wear? I think I have the WSM on disk, so I'll take a look.

worf928

I dunno. The noise is annoying - sounds too much like the motor pinging? - and the vibration is probably not going to make the t/o and pilot bearings too happy in the long rung. Also, with that bushing toasted the release are lever may vibrate when engaged - that will cause some shuddering, especially when reversing. (That's what my '91 did when that bushing vaporized.)

Procedure is to measure visible portion of release arm. Take note - measurement is different for S4 and pre-S4.

AO

Brett-

The worn bushing would have no bearing on the clutch slipping. Usually the only reasons for the clutch to slip are
1. worn friction plate (too thin)
2. Weak pressure plate
3. Contaminated surface (e.g. oil)

I do not believe there is a built in thickness indicator. Not sure the minimum thickness.

Jim bailey - 928 International

When the ball cup plastic bushing fails it allows the clutch arm to fall forward this changes the geometry of how the arm pulls on the release bearing. The off center pull at an angle distorts the springs on the pressure plate and as you try to engage the clutch the friction surfaces hit harder on top than the bottom and can easily cause shudder/ judder. Think of skipping a stone across the water...