e9stibi

I have posted this in the racers section but hope for broader input here:

I have a 993 4S with short ratio gear box (G64), RS clutch (96411601161) and flywheel that is currently used as a DE car. Due to a broken shift fork the gearbox was out 2 weeks ago and during the installation the shop checked the clutch as advised and they said it was still good and does not need replacement. The clutch slave cylinder has been replaced as advised by the shop.

Yesterday, I did an open track day with the rebuilt gearbox and the clutch started slipping after shifting from 4 to 5 under full throttle a few times (not always). It took 2 or 3 times for me to figure out that there is something worng.

I talked to my shop and they suspected the the clutch needs to be replaced and they were very surprised because the condition was so good when they had it out. The only thing that got me thinking is that the issue with the clutch started after the gearbox job. Is there anything that could have gone wrong when the "good" looking parts got reinstalled? Are there any things that should / can be checked before the engine is dropped again within 2 weeks for replacing the clutch disk (that might not be the problem ...)?

If the clutch disk needs replacement, are there better alternatives to the RS clutch? Some people on the track mentioned Sachs Sports Clutch.

What do you recommend and why? Should I replace other items of the clutch like the pressure plate? What are good sources to buy?

Thanks.

P.S.

Another observation was that I found a couple of oil drips when I came back yesterday. The car was sitting there for two weeks after I drove it back from the shop. The car was bone dry before the repair. The seals have been replaced with a standard gasket set. However, I did not have time to locate the leak.

Monique

I would start with bad installation; if you look up the part number, the (present) RS clutch is from the GT3 parts bin. They are very substantial.

GL

AOW162435

Disc installed backwards?


Andreas

JM993

The oil is your clue. Did they replace the RMS? Perhaps it, or the mainshaft seal is leaky. Either can contaminate the clutch and cause it to slip.

Good luck,
Joe

race911

Odd that it slips 4-5. Clutch discs generally can't go on backward, the amount of spline housing (for lack of a better term I can think of right now) would press it into the flywheel. I think. Remember, I'm no expert on G50 stuff because all of my G50 cars have not needed any work! But yeah we've pretty much all had "duh" moments on 901/915 clutches. Start tightening those pressure plate bolts, and.....uh.......oh yeah. But you get to it before the engine and trans are re-mated.

Oil leak? Can't tell you how many leaky trans mainshaft seals I've seen (especially the early 915s where you had to disassemble the trans to replace it) with really no evidence of oil on the disc surface. Ditto rear main seals.

chris walrod

The disk can be installed backwards but one would know it right away as it wouldnt release right from the start. Some time ago the disk's were labelled wrongly (for P-car installations) as they were also used in BMW applications where the way it was labelled correctly for the BMW.

Depending upon where the gbx oil leak is coming from, like mentioned above, this may be a reason its slipping.

e9stibi

Thanks for the reply so far. The invoice shows a seal package. It looks like I need to investigate the oil leak further. I will be still out of country for a week but have a good starting point.

If the oil causes the slipping would I see the clutch disk contaminated? What are other things that I should pay attention to when the disk is out?

Thanks

JM993

Likely. Just fix the leak, replace the disc and thoroughly clean the pp and flywheel and you should be ok.

Cheers,
Joe

Garth S

I had a similar slippage in my 928 dual disc unit last year .... top of power in 3rd and going for 4th: culprit was oil contamination from the RMS ('effin' mice built a nest of pink fiberglass, string & feathers over the winter - which packed in around the RMS on spring start up, and wicked oil out into the clutch pack. I found this out in a post mortum with the bell housing open).

The twin discs still looked great, so I ( stupidly) cleaned them with brake cleaner aerosol, block sanded them .... and reinstalled: don't do that!!!

Once the friction material is oil contaminated, it will slip forever, so toss it.

Second time around, installed new discs with the original plate(s), fresh RMS, and problem solved.

If the oil leak is at the bottom of the bellhousing, seals and a disc may be in your future.

race911

Thanks. I went and looked at an RS clutch/flywheel I have sitting around and sure enough not at all like the old ones burned in my memory.

chris walrod

Yeah, the offset side of the splined hub will bury itself into the guide tube even though the PP will appear like its clamped down and installed properly.

Only reason I know this is I had a friend do this. We were both scracthing our heads as to why the clutch wouldnt release.

e9stibi

How would you approach the dealership that did the gearbox job? You can imagine that I was not very excited after spending $$$ when I figured out that the clutch is slipping and oil is dripping after the job. What would be "evidence" of an installation problem?