Bradster928

This is about my 83 US 928, five-speed. I bought it a few months ago with 57K and now have 64K on the clock. It is my daily driver. I knew, or thought, it had some synchro issues (second, first, sometimes third, in that order). I have replaced the clutch master and slave cylinders and have properly bled the system. No issues there. The clutch seems to be fine as well.

Now to the point. Under the exact same conditions (speed, temperature, rapidity of shifting, clutch pedal travel), sometimes the car shifts perfectly and other times there is a severe grind when going into gear.

Wouldn't synchronizer issues be constant? Why perfect half the time and impossible the other half. So, I was wondering if there could be a linkage or some other issue not related to the clutch or hydraulic system?

Thanks!

Bradster928

Jadz928

What do you have to support if your clutch is fine? Does this include a properly adjusted intermediate plate? Search on this is you haven't already. Lots of good info, and often a mal-aligned IP is misdiagnosed as a syncro problem.

For others following along, this only refers to the early dual-disk clutch.

Re: your shift linkage. Felt fine to me when I last drive your car. Could inspect it closer by removing the shifter and checking play on the fore and aft rods.

Lastly, I wouldn't suggest a short-thorw shifter until you've remedied this situation. It will only exacerbate the problem.

Bradster928

Thanks Jim. I did not think of the intermediate plate. I'll search. But would that cause an intermittent problem?

Thanks again!

BRB-83-911SC

Having had similar symptoms, upon removal of my clutch during my recent engine pull we found the pivot arm bushing to be shot, and the splines on the central shaft to be dry. I would think that the pivot bushing being loose could cause incomplete/inconsistent releasing, and dry splines could cause the discs to drag. Also, the intermediate plate was a bit out of adjustment. While out, I also replaced the release bearing and clutch master cylinder (slave was new last year). I have not had the opportunity to test the fruits of this labor yet, but I expect to see improved clutch behavior. Whether my synchos have survived remains to be seen.

Do you have any symtoms of a dragging clutch - like the car creeping a bit with the clutch in, or a slight increase in revs when you pop it out of gear when at a stop? I had those, anthough intermittantly.

Bradster928

Thanks. I have not had the clutch dragging issue (I did for a while until I pressure bled the clutch hydraulics.)

So, I take it that synchronizer issues should be constant (correct?) and that my problem may be resolved with IP adjustment or new pivot bearing, also correct?

Thanks!

GregBBRD

Syncro wear is not intermittent. Clutch release can be. Don't drive the car if it is grinding gears...or you will need to solve both the clutch problem and replace the syncros you destroy from the clutch not releasing.

Short throw shifters on the "Porsche Style Syncro" gearboxes suck. The amount of effort required to move the slider over the top of the actual syncro requires a good amount of leverage.

WallyP

"So, I take it that synchronizer issues should be constant (correct?) and that my problem may be resolved with IP adjustment or new pivot bearing, also correct?"

Yes.
Perhaps, but there are other possibilities.

It is not unusual for years of wear to create "steps" on the central shaft. The clutch disks then may hang up on the edge of the step and not pull away from the flywheel or the pressure plate.

Or, the central shaft may just be dry/rusty/dirty and not allowing the disks to float freely.

I would suggest that pulling the clutch and carefully inspecting everything would be a good first step.

Use great care to avoid dropping the heavy assembly onto any part of you.

Dave928S

I agree ... many little things can add up to one big problem with these clutches, so you're best to pull it out and check everything. You'll get all the assistance you need here to get it right.

Here's a pic of the stub shaft with the wear line, that Wally referred to, just visible and highlighted with a line. When the step becomes more pronounced and the shaft is dry, the disk movement can be impeded by the step. Add a maladjusted intermediate plate, and perhaps a few other small problems and it becomes a total mongrel to operate cleanly.

Mrmerlin

if you have not already done so replace the flex line for the clutch this line can swell when it gets hot and then the clutch will not work properly,
it is one of the things that gets overlooked when doing clutch repairs, also there should be a heat shield fitted to the exhaust manifold this will protect the line from getting hot

Bradster928

Thanks to you all. As always great advice and good places to start.

depami

I second that even though it’s not my thread.

I have similar experience.

I bought this clutch and transmission thinking I may have syncro issues.

https://rennlist.com/forums/928-foru...brand-new.html

I know my clutch is now toast as it squealed and “threw parts”.

My original plan was to change both and TT bearings too but maybe I’ll just do clutch first and see how it shifts then decide about the rest.

mark kibort

I have found short shifters are fine, its really style, and synchro wear that determines shift ease and correctness. an intermediate plate will show up at idle , putting the car in to gear, and not as much once you are driving, mainly becuase there is such little friction due to misadjustment. big problem at a stop light, but no issues on the track, or drivig faster. (a little knotchy, but nothing to write home about)

synchros performance are heat related, and will change to the better when hot, and get worse when too hot.

ive raced and driven all types of the 928 gear boxes, and i think it too me about 10 years of street driving to get the early box shifting correct. still on the track, it is a challenge , if the synchros are worn.

double clutch , etc, wont solve the problem. get an 85 box, or learn how to be very very smooth and RPM drop sensitive.

Dave928S

^^^ Your experiences are different than mine. It didn't take me ten years to get my 82 box shifting correctly ... it just took a few hours to get the clutch and gearbox setup and adjusted correctly, which had been played with by so called experts previously. An early box can work just as well as a later model one ... how do i know? ... check my signature.