Hello fellow Porschephiles!

Installed a new clutch disk between two used but in good cond surfaces.
The flywheel surface appears near new and measures new according to specs in the Porsche "Technical Specifications" book that I have. The pressure plate surface also appears near new and is the type 215 Sachs. The disk is also Sachs and measures 10mm thickness. Pilot bearing is clean and well lubed. Input shaft is straight and true. There is no oil or grease on any of the surfaces inside the bell housing, on the back of the engine, or on any of the clutch parts. Side shift trans has new lube with all new seals. All shift rods and junctions are in excellent cond. Using Rennshift shifter. Trans shifted fine before switching to new disc.

Installed new clutch cable. Pedal bushings are good. Cable pulley is good. Cable adjusts well enough.
BUT!
clutch will not fully disengage, therefor no shifting can be done.

I removed the trans yesterday and swapped out the pressure plate while inspecting all surfaces and checking to make sure the pilot was not being jammed some way. Put it all back together, still cannot shift, clutch will not fully disengage; and with a better pressure plate installed this time, the shifting is even more difficult, as the plate is a bit better than the first one. Adjusting the cable to full tight has no effect. Setting it to 1" pedal play works the same as fully tightened cable, no pedal play. Stepping on the pedal makes the clutch slip, but does not fully disengage, no mater how the cable is adjusted.

Mega frustrating.
Is the disc too thick?, The clutch worked and shifted with the used disc in it. Old disc was about 9mm thick, thinner due to age ware. The new Sachs disc measures 10mm. I also have a rebuilt Sachs disc that measures 9.8mm, and several used discs measuring between 8.5 to 9.5mm.

OR?
Is the pressure plate faulty in some way.

Once again, the critical dimensions of the flywheel are correct for use with these parts. Of the above two possible faulty components, the pressure plate seems to me to be the culprit.
How can a pressure plate be faulty?
Warped surface
Scored surface from clamping onto the exposed rivets
faulty diaphragm spring, not levering the plate away from the disc far enough

Seems to me the only possible problem could be the last of the above three potential
problems. The second of which does not exist.

So it is really that I need a new pressure plate?
Can the diaphragm spring be wore out? bent around it's fulcrum ring? Incapable of levering the plate to free the disc?

Your comments are welcome.
Thank you!

Greetings from Munich!

This is my car Ed is having this very frustrating issue with. Your expert advice and time to offer it are much appreciated!

do ya reckon the da problem is y'all?

Have a great weekend!

Mike in Munich

There is a pivot in side the bell housing that is adjustable by shiming it in or out. You maybe able to get more adjustment there.

Thanks for the suggestion Joe. Any other ideas? This is so strange!

Mike

Clutch tube mount in the tunnel could be broken. See if the tube moves when the pedal is depressed. Make sure the cup bushing is in the clutch fork.

Sorry to break in but I'm having the same problem. Just so I understand, there should be absolutely no movement in the clutch tube when depressing the pedal? Mine moves about 1/4 inch side to side but feels well anchored if I try to move it with my hand. Any other way to test for a detached tube?

Thanks Bruce!

Before you chase your tail, have someone push the clutch to the floor and hold it, or use a stick to to that.

Get under the car and see if the clutch release fork is almost touching the rear of the slot it in at the case.....

Somewhere close to 5 mm or less.

If it is close, your problem requires you pull the tranny.
If it is not close, the problem exists between the pedal and the release fork.
Diagnose it a bit before you chase your tail.

If it worked before you replaced the clutch, it may be you mounted something wrong like the throw out bearing, or the clutch is not aligned properly, or the drive shaft going into the crankshaft is full of rust and not properly greased, or what you think is a good working pressure plate is broken and needs to be replaced.

Rich

Thats good thinkn, and a long shot. I resolved that issue about a year and a half ago. the tube was slopping around in there. I fixed it by clamping it to the floor of the tunnel with a custom make "U" clamp, with a hole on each side of it, just like a copper plumbing clamp for 1/2 cu tubing.

The only thing it did for me however, was to keep it from interfering with the movement of the shifter. It had also come loose in the back of the tunnel where it had originally been brazed to the hole in the steel sheet it passed through. A bit of weld now holds in in place again back there, with some sealant to keep out water.

Seeing it break away like it did is proof how much stress it is under from daily use.

Thanks for your reply!

This makes perfect sense. Surely if it cannot travel back any more than it does, it would prevent the disengagement from happening. My guess is you have nailed it. Every other part of the system is good.

The solution then, it is likely shims under the pivot ball will give it more room to travel backward. Very clever, someone had to sort that in the past, and put in this design element.

Thank you kindly!

This is likely the problem. I believe Mike may have mentioned this to me yesterday when we were discussing it. Phone signal here is usually not so good, and I may have mis interpreted what he said, so it did not hit me as relevant, what it very relevant.

I will be out there in a few checking the distance the fork arm is from the port it passed through on it's back side. Probably hitting it now.

Thanks All!

Presently, there is only 5mm space between the fork arm and the back side of the port it passes through when the pedal is not being depressed.
Depressing the pedal makes the arm stop against the mag case.

Time to take the trans out again. How much shim will be necessary? I will try a 2mm shim to start. The parts charts show a standard 8mm id washer 2mm thick with 20mm od.

A ghost from the machine came to me last night, reminding me that when I had first taken this engine/trans set apart, someone had installed shim washers between the flywheel and the pressure plate at each bolt point, thereby solving the problem for themselves. At the time I could not imagine why they had added the washers in such a place. Now I know why.

Thank you all!

I don't get how one system can vary from all the others.

M.i.M.

The trans came out in about 45min. The ball pivot point was machined deeply into the mag case. This was the problem. The ball was screwed in so deep, it was necessary to chisel material from around it so I could get a socket on the unusually short hex portion of the part. After doing so, removing the ball revealed a seemingly "too short" portion of thread. The shortness of it meant I could only add a short stack of washers to get me near where I needed to be.

The fork extends beyond the pivot point 2". The arm extension of the fork extends out to the cable about 7" from the pivot point. Adding 3mm shim (two 1.5mm washers added) meant I would pick up about 10.5mm extra travel over the way it had been.

This turned out be be sufficient, but not necessarily optimal. The trans shifts fine now; the clutch fully disengages in the normal manner.

Once I had removed and reinstalled it once, the second time around took less than 1/2 the time it took the first time. Having a trans jack makes a big difference. It took more time to figure out what to do about the deeply seated pivot ball, than it did to remove the trans. Putting the trans back in is more strenuous; it likes to be perfectly aligned before slipping back into place.

Job accomplished, now for the dead newly rebuilt alternator.

Thank you all!

A final note here which I wish someone had mentioned, was that the ball cup bushing at the pivot ball, which screws into the bell housing should have been replaced. I was just told by Julian Avent, owner of 911 Werks in Killeen, TX...who saw a photo of Ed's (Bangoos') shim-mod, that the worn-out bushing was the culprit all along and had it been replaced the 3mm shim (2 washers between the ball and the bell housing) wouldn't have been necessary and are in any case a BAD way of correcting the problem.

Apparently there are now about three threads fewer (of about 8) which are screwed into the trans, and this piece has A LOT of pressure on it. It can break, which I now have to hope it won't. I wish Ed had changed that nylon bushing. It sells at Pelican for $7.

M.i.M.

Replace the pivot clip too. While you're in there....