4corsa

Regarding my '87 944 with 190k miles (bought last spring). When in higher gear under heavy acceleration (especially from lower rpms), there is a significant vibration from the rear end. The vibration is relatively low frequency - similar to a wheel out of balance at 40 mph. This is especially noticable in 4th gear accelerating hard from 2500 rpm - almost feels like a driveshaft way out of balance. It is much less noticeable in 3rd gear and 5th gear, and non-existent in 1st and 2nd gear when accelerating.
My independant Porsche mechanic (i-Service, Cherry Hill, NJ) believes it is the engine overpowering a worn clutch. Does this sound right? I will add that in extended stop and go traffic the clutch will overheat and chatter when leaving from a stand still. The clutch is has approximately 90k miles on it. I may consider investing the $$$$$! for a new clutch, but don't want any chance of this problem not being fixed after the investment.

V2Rocket

Exhaust rubbers tend to harden and the booming exhaust transfers to the car...I need to replace mine.

Tom M'Guinn

If you can feel it in the gear shifter and/or clutch pedal between shifts, that would support their diagnosis. On the other hand, are your tires all balanced well?

4corsa

Thanks. I had the same thought. I BARELY feel it in the shifter. I had new tires installed a month ago. Same before and after. It only does it under acceleration. In looking at a parts diagram, i noticed there is a "drive shaft vibration damper" - wonder if mine is worn out or something. Or perhaps the flex disc that attaches the transmission to the driveshaft?

zerMATT951

I had a strange sensation in my car after having the clutch replaced that was tough at first to isolate, but I eventually spotted where one of my exhaust clamps was contacting the under-body on hard acceleration. Mine was a clamp where the waste gate ties into the exhaust. It was a simple fix to loosen and rotate the clamp a bit so that it didn't make contact. My exhaust is aftermarket, so that type of problem may not exist with a stock exhaust, but it may be worth spending a few minutes under the car looking for possible contact points or hard rubber hangers as was suggested above.

John_AZ

Confused??

Do you have an automatic?

Flex disc..

http://www.pelicanparts.com/cgi-bin/...uto%20Trans%20

But you said ...."the clutch has 90K miles on it"

J_AZ

4corsa

No automatic, 5 - speed.
I didnt realize the flex disc is on automatics only.

mblaszak

You have already identified your own problem... you have said that your clutch slips...it should not slip, ever!!! So, time to go in there and put in a new clutch assembly as well as a properly resurfaced flywheel.

mytrplseven

I recommend going with the Sachs spring plate as opposed to the old "rubber donut" You'll feel a minor vibration in the shifter but It's the proper way to do a clutch replacment.

VirginiaF1

Corsa, have you inspected the clutch viewport yet for any indication of wearout?
See Clarks Garage for access.

4corsa

Thanks very much for all your input - much appreciated!
Looks like a new clutch will be in order (agree that the spring type is the way to go). Time to open a new savings account...

VirginiaF1

Glad to hear a diagnosis mate...
What proved definitive in determining a new clutch required?

joes

I would check for wheels out of balance. loose cv joints, bad rear wheel bearings/ loose lug nuts. Balance shafts out of time can cause some weird vibrations. Put it up on jackstands and see if it is still there. I have never experienced an "over heating clutch" unless you are street racing or something. Clutches usually slip.

gtroth

Might as well do a clutch wear measurement, heh?

UMDgrad

How much are we talking about for a new clutch? Done the "right" way, on the OP's 944.