CBR944

I'm pretty sure Hacker and others have answered this in earlier posts, but pressing the clutch pedal disengages the clutch and disconnects the torque tube and transmission from the flywheel. So with engine idling and in neutral, press in and hold the clutch down, wait a few seconds for the torque tube to spin down, then engage reverse. If there's grinding, that means the torque tube is still turning: the clutch is not disengaging. Your problem is with the clutch mechanism and/or hydraulics.

928Collector

Thanks.

I have several 5 speed manual 928s. 2 of which still have this issue. One of which has had the transmission pulled. Another of which I believe i got duped into replacing the transmission for big $$$. I didnt know it at the time but replacing the transmission isn't that difficult. and I got burned by a West Palm Beach indie that redid my clutch for $$$ because i trusted his view that it was a clutch issue.

There seems to be a variety of diagnostic tests that can be done outside of the car. So i'm trying to determine these tests for the benefit of 5 speed manual owners as well as myself to be better educated about going in surgically, on a judicious budget, in an informed manner on repairs.

Yes, 1st/Reverse gear grinding is a blend of issues. But some of these issues can be diagnosed for free hence this information/notes compare share. And apparently some repairs can be done inexpensively - a friend gave me one that quieted things down but wasn't the silver bullet. I'm looking for a very precise/mechanical, step by step diagnosis process for the benefit of all. I think once this issue is gone 5 speeds will continue to appreciate in value. .

All thoughts/comments/criticisms welcome - I'll organize things for the benefit of the community.

hacker-pschorr

If you have multiple 5-speed 928's (like I do). Do what I did 20 years ago. Get a used lower bellhousing (they are cheap) and cut a huge hole in it. Now on the lift someone can work the clutch and someone else can see what is going on.

This has saved me from countless frustrating days.

I curse Porsche for not doing this from day one. For how well engineered this car is, complete and total fail not having an inspection / adjustment method. My fab shop is currently making me another one with a removable plate, if this works I'm doing all 4 cars.

Mrmerlin

I made one of those as well,
and used the piece I cut out to fit back in ,
with a few rivets and pieces of sheet metal

928Collector

Gentlemen: I've summarized the comments above.
Please comment, critique, add as we're getting close to resolving this very common issue.

The clutch is not releasing and is causing the "gears grinding (only) in 1st and Reverse

As only reverse and 1st grind, and as reverse does not have a synchro, the clutch is not fully releasing, disengaging or is dragging. This is evidenced by the fact that reverse has no synchro.

Pressing the clutch pedal disengages the clutch and disconnects the torque tube and transmission from the flywheel. So with engine idling and in neutral, if I press in and hold the clutch down, wait a few seconds for the torque tube to spin down, then engage reverse. If there's grinding, that means the torque tube is still turning: the clutch is not disengaging. Therefore the problem is with the clutch mechanism and/or hydraulics.

Any single part in the clutch system could be causing the clutch to not fully disengage.

• Hydraulics
  • there doesn't have to be a leak for the master and or slave to not be fully functional
• Intermediate disc not holding adjustment
• Clutch disk has failed to a point where it's frayed and continues to rub even when disengaged
• Release bearing failure
• Pressure Plate failure
• Lack of proper lube
• Clutch shaft is damaged
• Upper ball / cup issue
• Improperly bled

There is no hydraulic "adjustment" on 928s. Instead there is a hole in the bottom of the bellhousing that allows you to see if the slave rod is moving the full distance. The slave rod is probably not moving the full distance.

If not the slave rod, then it could be the slave, master, the line connecting them (or all three) have air in the system.

Or it could be the intermediate disc. The intermediate disk has three adjustment tabs on them to "center" the disc between the two friction discs. There is some debate on how to do this, I cheat:
https://rennlist.com/forums/928-foru...ch-owners.html
When those three adjusters wear out, that center "disc" floats back and forth causing the clutch to drag. One solution (which I did on my 79) is replace the rivets:
https://rennlist.com/forums/928-foru...l#post18924701

Or it could be something as simple as the hose that connects the slave / master was installed incorrectly and has a low spot preventing that one last air bubble to burp out.

Or it could be:

• The clutch master had failed
• One of the clutch discs is badly frayed
• Release bearing housing is physically broken
• Proper grease on the shaft (it was dry as a bone & pitted) - must use proper grease here
• Pilot bearing was shot

See this thread:
https://rennlist.com/forums/928-foru...n-my-78-a.html
Here's a trick to installing the clutch master:
https://rennlist.com/forums/928-foru...he-fender.html

This makes adjusting the clutch super easy:
Solution: Get another bell housing and cut an access / viewing window in it.
Mount the clutch slave cylinder to the lower bell housing unit with the access/viewing window.
Put the car on the lift and have one of your guys run the car through the gears as we watched from below to see what is going on.
While the intermediate plate can be adjusted with the housing off and without operating the clutch, being able to operate the clutch AND tweek the adjustment at the same time could be very helpful.

SwayBar

What is the follow-up from removing and repairing the trans - what work was done?

Is the problem still unresolved, or has it been fixed?

WestInc

I did a smaller inspection hole with a plate. Works great but Hacker Pschorr's big hole obviously has better access...

928Collector

Gentlemen:
One diagnosis / fix that came back on my 1979 5 speed grinding in 1st and Reverse was a Shift Collar + 1st gear set replacement.
Any thoughts/views much appreciated.

Rob Edwards

What kind of wear do you have on the gear that warrants replacement? Bad dog teeth wear? Pics would be worth many words. Precision Motorwerks has remanufactured dog teeth, though I'm not sure for early gear sets.

928Collector

The blue arrow is the shift collar that was sliding. Please let me know your thoughts on the gear teeth. I've been burned before on this issue and I get a number of differing diagnosis anywhere from something in the clutch to i need a rebuilt transmission.

Rob Edwards

That's less than a 3x5" photo at 72 dpi, I'm afraid I can't see anything. Got any high(er) res pics?