dfinnegan

Today, for the first time ever, I noticed my clutch slip at high revs. Not at all at lower revs or when shifting to a high gear at low speed.

The clutch was replaced by PO at 27k miles and I'm now at 54k miles. I've had the car since 36k miles and don't believe I have been hard on the clutch. I've never replaced one on any car before and generally drive 100k+ miles per car.

Two recent events are worth noting:

1. Hydraulic Fluid Bleed
2. Other Driver

You may recall a recent thread in which I described problems with a hydraulic fluid bleed. The shop's bleeder went south and I got a bad bleed. The brakes were re-bled and are fine. The clutch slave cylinder was also re-bled, but I could not see the action so can't vouch for how well this was done.

Also, last week I let a friend drive the car and he ran a couple of fast hard starts. I don't know if he was slipping the clutch, but it seemed worth noting.

Now, Questions:

1. Could a bad bleed on the clutch slave cylinder cause these symptoms?
2. If my friend did slip the clutch could this cause the symptoms and, in this case, will they go away?

Or, am I simply grasping at straws and am looking at a new clutch soon?

Heirsh

My clutch will slip when shifting from 2'nd to 3'rd quickly at wot. Po replaced the clutch 58,000 miles ago. I've put 28,000 miles on it and its always done this. I've thought since day one, "dang I'm going to need a clutch", but it just keeps going.

I am not sure what I am actually telling you here, but perhaps its not as bad as you may think. :/

TR6

I had similar symptoms previously and it was a result of the clutch pedal not fully returning to upright position when released. It could be caused by either hydraulic problems (bleeding) or the mechanical linkage in the pedal.

Heirsh

Yeah I pulled my pedal assembly apart, checked everything. Replaced the master and slave clutch cylinders (they aren't expensive). I rebled it several times, to no real avail, other than making the pedal a good bit easier to push in (thank goodness!).

For me I think I just need a clutch. I hope Dave's problem is less severe. Given the mileage and such it seems likely?

dfinnegan

Thanks guys. I'll have a look as time permits and try and sort through the mechanicals and do a re-bleed. Keeping my fingeres crossed that I'm not in for a clutch so soon.

viperbob

The whole clutch hydraulic system is designed to release the clutch. If you have been having issues here, you may not have been fully releasing the clutch in the past. This can cause premature wear. In any case, if your clutch is slipping it is not going to get better. The fix is to replace it. Sorry.

dfinnegan

Bob,

Is it possbile that something is wrong with the system that it is not fully releasing the clutch?

I'm confident that I am not riding the clutch or, otherwise, failing to release it. If this is what's happened then there must be something mechanical that is causing the clutch to not fully release. Is this possible?

Thanks,
Dave

Staffan

Hi, I had problems with a slipping clutch a few years ago.
Turned out that the clutch was just a litt bit more than half worn but had oil on it.
I changed the gasket between the engine and gearbox and had no clutch problems after that.

dfinnegan

Turns out I needed a new clutch. I've had it replaced.

It was determined that the clutch was hanging up which caused premature wear. Apparently this is a known issue with 964s. Or, at least, it has been known to happen to other 964s. There are needle bearings and bushings which get rusty and don't allow the clutch to fully disengage. The fix is to modify the mountings with a bit of machine work and replace the setup with a 993 type which has improved bearings and bushings. I think I've gotten this right.

It seems likely that this problem existed before I purchase the car as evidenced by receipts for two clutch replacements by the PO within a few thousand miles of each other.

At any rate, the clutch is noticeably improved and holding like a champ.

JasonAndreas

I hope they didn't charge you for machine work? The bearings and bushings for the 964 and 993 are exactly the same, it was the G50 prior to the 964 that had problems. And if they did try to machine the transmission bellhousing the alignment portion of the special Porsche bore enlarging tool is actually ~5mm too small for the 964 (964=19mm and prior models were ~14mm) so they would have had to freehand align the clutch operating shaft ears/bores. A more common problem for the early 964 was corrosion on the guide sleeve causing the same problem you experienced. That was one of the reasons why Porsche modified the release bearing towards the end of 964 production.