Diagnosis Request
#1
Diagnosis Request
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 $$$$$! for a new clutch, but don't want any chance of this problem not being fixed after the investment.
My independant Porsche mechanic (i-Service, Cherry Hill, NJ) believes it is the engine overpowering a worn clutch. Does this sound right? I will add that in extended stop and go traffic the clutch will overheat and chatter when leaving from a stand still. The clutch is has approximately 90k miles on it. I may consider investing the $$$$$! for a new clutch, but don't want any chance of this problem not being fixed after the investment.
#3
Rennlist Member
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?
#4
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?
#5
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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.
#6
Proprietoristicly Refined
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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 $$$$$! for a new clutch, but don't want any chance of this problem not being fixed after the investment.
My independant Porsche mechanic (i-Service, Cherry Hill, NJ) believes it is the engine overpowering a worn clutch. Does this sound right? I will add that in extended stop and go traffic the clutch will overheat and chatter when leaving from a stand still. The clutch is has approximately 90k miles on it. I may consider investing the $$$$$! for a new clutch, but don't want any chance of this problem not being fixed after the investment.
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?
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
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#8
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Join Date: Feb 2004
Location: Blaszak Motorsports
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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.
#9
Drifting
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.
#11
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...
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...
#12
What proved definitive in determining a new clutch required?
#13
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.
#14