Johnny G Pipe

Hi again friends.

I bought a rough 79 5 spd in the South of France and drove it to Scotland, in an act of faith/bravery/stupidity. I will get round to posting the story I promise.

In the meantime, at the first gas station the car would barely start, and this continued all..the...way..home. Turns out it was 3 evils all at the same time: ignition switch, bad battery earth and non return valve at the fuel pump. All fixed now, starts great.

Anyway, I had to bump start the car probably a dozen times over that trip. When I got it the clutch action was good, no problems. Now I am using the car regularly, the clutch bite point is really high on the pedal - right at the top, I get judder getting going in 1st and reverse, and I get the rattling noise when the car is idling with clutch out (disappears when clutch in).

The car shifts gears fine when on the move, no dragging or slipping.

Searching for clutch related stuff has opened a 928 chapter labelled 'expense, frustration, voodoo, more expense' it seems; - so can anyone give me any starters?

The Forgotten On

I would inspect the wear of the clutch plates with a micrometer to ensure they are within spec, same goes for the flywheel.

This will mainly determine how much of the clutch is left and if it needs to be redone. More than likely if the car has 100K or more miles on a original clutch.

Next is to look for anything that may look damaged such as the pressure plate.

It also wouldn't hurt to give it a service, regrease everything, and adjust everything per the work shop manuals to ensure proper function and prevent transmission wear.

Can't wait to hear your story on your journey back to Scotland.

Johnny G Pipe

Thanks - the car has around 70k miles but has been neglected. Is it correct that these items can all be inspected and measured from the inspection port without any dissassembly?

The online WSM I use https://www.manualslib.com/manual/39...8.html?page=1# is not easy to use

Mrmerlin

remove the air cleaner and inspect the release arm bushing,
i will bet its toast,
NOTE this may require you to drop the clutch to replace it

Johnny G Pipe

Thanks, remove air cleaner?!, OK.

I found guidelines for checking the plates BTW

https://www.porscherepair.us/porsche...tch-discs.html

docmirror

Another vote for the pivot ball or plastic ball cup bushing. Wear item anyway. Common failure.

JBGold07

Subscribed.

I also have shuddering at biting point. I have noticed mine works perfectly when cold, not shuddering or noise. When warm it has juddering and noise as you describe. I have a lower biting point though.

I was assuming pilot bearing, thrust bearing need replacing and some refreshed grease would help etc old grease causing it to hang up on engaging? I haven't gotten to do this yet.

I did replace the pivot bushing, it didn't help but it did need replacing.

On reflection the last thing I touched before all this was rebuilding the slave, I will be rechecking that for correct parts and fluid change before going deeper.

I won't get to this until winter though so will be interested in your progress.

Cheers

docmirror

Shuddering on engagement is a different symptom, and likely a different cause. I would inspect the friction surface of the clutch plate(s), and the condition of the pressure plate and flywheel. Usually one will find some kind of contamination, or damage where the friction surfaces meet the metal. Also can be caused by broken spring fingers in the PP asm.

James Bailey

Missing bushing changes the geometry of the clutch arm and distorts the pressure plate. That causes the friction discs to hit first on one side and skip or judder....very common problem..
Obviously broken spring fingrrs will cause similar shuddering due to uneven pressure on engagement.

SwayBar

I've done this without dropping the clutch.

It can be accessed with air filter removed, and using a long beefy screwdriver and pry-bar to manipulate the release arm off, then back over the greased, new bushing.

Tricky for sure, but good if you don't need to remove/replace the clutch.

With all that said, it sounds like you do need clutch work of some type.

Johnny G Pipe

OK, thanks again. The hunt starts under the aircleaner, but next need to take off the bellhousing plate.

Should have bought an auto..lol.

Mrmerlin

the reason i have suggested clutch removal is that the early cars have a smaller opening for the release arm the last bushing I replaced i was able to unscrew the ball and then open up the bushing opening with a dremel and it made it easy to push the bushing onto the ball then I screwede the ball back into the bell housing all this working from the top.

IIRC another owner of early cars had a similar issue and they removed the clutch to replace the bushing.
Later cars 84 on seem to have more room to work

Wisconsin Joe

Ok, my $0.02 (worth what you pay for it).

Shaking and shuddering can be a variety of things. From the arm bushing (cheap & easy) to the friction discs, PP and Int plate (not so cheap).

The "squeaky, squeaky" when the clutch is released (pedal to floor) is likely the pilot bearing (cheap, but not easy). Keep in mind that the pilot bearing is the only piece that spins when the clutch is released, but not when it's engaged. The Throw Out Bearing spins all the time, although it does have different forces on it engaged vs released.
When the pilot bearing goes, it sounds really bad.

Given the symptoms you have, I think dropping the clutch is going to have to happen. On the bright side, the 928 has the easiest clutch removal I've experienced. No need to pull the motor or drop the trans. Just remove the Bell Housing and the clutch just unbolts.

Follow the WSM and you're good to go. If your copy of it isn't very good, there's a link in the "New Visitor" sticky that has a usable version. Alternatively, Roger sells a CD-ROM copy that has the full WSM and a whole lot more.

And to answer your original question:

I doubt it. Bump starting the car can put unusual stresses on the clutch. But it sounds more like the car sat for a long time and simply using the clutch has taken it's toll on the marginal parts.

Johnny G Pipe

Thanks, I was hoping I hadn't killed it :-)

This is a theme on this car. There was NO bushing left in the rear shifter linkage when I got it. Made for interesting shifter behaviour..

Wisconsin Joe

The thing is 40 years old.

I'm guessing a lot of stuff is worn out.