PD69

I recently began hearing/feeling some rear end grinding/vibration sounds as if its emanating from near the gearbox seems to happen mostly when decelerating in 3rd and 4th gear car has 106K miles and has been well serviced any thoughts????

ErichCS

By well serviced do you mean the clutch has been done? If yes that then the next obvious thought is transaxle, doubtly cv-joints or wheel bearings. Of those three my guess would be transaxle. Has the transaxle oil been changed in there recently?

Oh yea, it could also be the torque tube, but that noise would probably only vary with engine speed. Give us some more information i guess...
Erich

PD69

yes the manual tranny oil was just replaced 30 days ago the grinding/vibration is coming from the center of the rear not on the outside ie wheel bearings

ErichCS

Any chance whomever did the clutch forgot about the pilot pins between the torque tube and transaxle when remounting the transaxle? I've heard forgetting those dowels/pins can lead to tranny failure quickly... just an idea. Whatever the problem is it def. sounds transaxle related.

Erich

PD69

Erich not sure about the clutch pins/dowels I do know it was replaced at 80K miles by the previous owner I do have the records the vibration occurs on accelerating thru 2-3 gears 4-5 are smooth no vibration and all is well cruising along at 45+ mph when it vibrates most is when I'm in 2-3-4th gears and decelerating when I take my foot off the throttle and coast when I coast is when I feel it most all the time..... thanks for your time and feedback!!!!!

ErichCS

Maybe it's just syncros or some other tranny thing that i'm not that familar with.

One more question - Any chance your car has LSD and the proper tranny oil wasn't put in there? I think maybe this would maybe affect the car more while accelerating rather than slowing down. I think maybe you should just have your shop take a look at it. It could be hard to properly diagnosis this noise. Any rennlisters in your area? Where are you from?

Good Luck!
Erich

PD69

I have 2 appts set up for next week not sure about the LSD will find out next week can the wrong tranny oil affect this potential problem???? the tranny oil was changed approx 30 days before this vibration thing started I cont to drive my 924 everyday the vibration does not appear to have gotten worse.... go figure..... thanks again for your feedback Happy Holiday weekend!!!

ErichCS

Don't forget to let us know how it turns out for you...I'm really curious on this one.

Good Luck!
Erich

special tool

Check center cv bolt tightness

PD69

My clutch is fried confirmed by 2 seperate Porsche techs apparantly the clutch has a rubber dampening component not good... this latest clutch lasted 25K miles I'm going to replace with a metal spring loaded Sachs I hope I spelled that right... what's amazing to me is that the clutch sits on the engine but the vibration was coming from the rear end/gear box apparantly it goes out of balance resulting in rear end vibration hopefully I have no other problems! Thanks again for all the feedback!

special tool

It is not really a vibration when a rubber clutch goes out. You will hear a loud click when you let out the clutch in first as the metal safety teeth on the engine side of the clutch are now all that is moving the car. When the teeth engage, they stay engaged, they do not cause a vibration.

The best check for broken rubber clutch is to jack up the rear and put it into first. You will be able to rock the rear wheels back and forth about 70 degrees of motion until you hear a loud click. If the clutch is good, you will only get maybe 10 degrees.

ErichCS

25K Miles and the clutch is gone?? Is this a street car? I know age can also be a factor in causing the rubber centered clutches to break down over time. But wow i'm amazed at this one. It seems to me that your problem is more tranny related . . . There have been a couple of good ideas or points to consider before dropping some cash on a clutch, are you the hands on type that will check these yourself? Or are you just going to go for the clutch? there are other ideas and tests you could do yourself to see where the noise is coming from...

If youd like some more suggestions let us know. I just want to make sure the clutch is actually the source of the problems here.

Good Luck!
Erich

Manning

I've seen pictures of grenaded rubber centered clutches, and sometimes when they go, hunks of the rubber will actually spin out and act like a pendulum, causing everything to go out of balance (vibration). I guess this vibrations could transmit down the torque tube and seem like it is coming from the rear end. And if the car has 106K on it, the always overlooked trans mounts could be perished by now and allow the vibration to be amplified even more.

PD69

that sounds like the problem at least thats what the techs say I guess it makes sense given the rubber nature of the clutch how did this design flaw get by the Porsce engineers?????? cie la vie....... thanks for the note

PD69

another note to all apparantly my torque tube rotates 60 degrees this should not move at all according to the techs supposedly this is another indicator of a failed clutch system