'91 929S Low speed vibration
#1
06-12-2005, 02:36 AM
'91 929S Low speed vibration
My car is experiencing a low speed vibration at about 15 mph. It is very low frequency, almost like a shudder or wobble, and disappears quickly. I have checked the u-joints, center bearing cushion, CV shafts, and various mountings...nothing appears loose. The trans is not slipping. Feathering the throttle or pushing it harder reduces this effect, i.e. the quicker you get past this speed the quicker it is gone. I haven't noticed anything else strange. Could this be coming from the differential? I'm not sure if this is a limited slip unit or not. I am open to any ideas.
[IMG]local://upfiles/996/3C8A1EDBE2FC4C9793B4AE772D80BB9F.jpg[/IMG]
[IMG]local://upfiles/996/3C8A1EDBE2FC4C9793B4AE772D80BB9F.jpg[/IMG]
#3
06-15-2005, 09:17 PM
RE: '91 929S Low speed vibration
Have you checked the inner cv joint when worn there can vibrate, mostly when
just starting from a stop. Check both output shaft at the diff, for play in and out. When you said, you checked the u-joints did you remove the driveshaft
to rotate each joint. Often if you just check by trying to twist the joint for freeplay while in the car there'll seem ok. The best test is to remove the shaft,
if you have a worn joint it feel as if one spot is worn flat or notched.
just starting from a stop. Check both output shaft at the diff, for play in and out. When you said, you checked the u-joints did you remove the driveshaft
to rotate each joint. Often if you just check by trying to twist the joint for freeplay while in the car there'll seem ok. The best test is to remove the shaft,
if you have a worn joint it feel as if one spot is worn flat or notched.
#5
06-16-2005, 03:25 PM
RE: '91 929S Low speed vibration
hear hear blueman, it sounds to be most definately a balance or rotation problem. 99% of shaking or wobbling in steering or general comes from improperly balanced tires, easy 20 dollar fix at walmart or local tire repair shop.
#6
06-20-2005, 03:15 AM
RE: '91 929S Low speed vibration
Its actually a transmission shudder, it seems. Adding a friction modifier didn't eliminate it but it reduce it signifigantly. I doesn't seem to do it when the car is cold, only after it warms up.
#7
06-20-2005, 03:17 AM
RE: '91 929S Low speed vibration
Its actually a transmission shudder, it seems. Adding a friction modifier didn't eliminate it but it reduce it signifigantly. I doesn't seem to do it when the car is cold, only after it warms up.
#8
07-15-2005, 03:34 PM
RE: '91 929S Low speed vibration
I had the same problem, but it was a tire out of round. Once I replaced the tire the vibration disappeared.
Now since you said it was a tranny shudder? Here's a thought, perhaps your driveline is slightly misaligned.
Now since you said it was a tranny shudder? Here's a thought, perhaps your driveline is slightly misaligned.
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