major vibration

[s-man]

1986 951, 79k miles, have been faced with a vibration coming from the rear.

This vibration only becomes noticeable when the vehicle is put under moderate to heavy load(not luggage).

If I drive the car easy up through the rev range , then the the vibration is really not a factor. Once a heavy load factor, matting the accelerator and intoducing boost factor, the vibe is not pleasant to say the least.

At idle the engine runs smooth, standing still if I raise the throttle through the range, the engine remains smooth.

Up until today I had been lead on the path of potential clutch breakdown, the rubber damper dilema, but yesterday I spoke to a wizard in the repair end and suggested looking at the transmission mount supporting the tail end of the transaxle.


I had the car up on the hoist today, trying to visually inspect the mount, this is a prticulary difficult task, very hard to eye it up. I reverted to moving the tranny by hand side to side.

The tranny seemed to move in a side to side direction with not much force. I haven't seen much discussion on the bourd here in regards to tranny mounts, and the only one that did, say's this is normnal. I am of a differing feeling.

From my understanding only 3 mounts support this driveline, 2 engine and the last the tranny..

Any suggestions????

Please Help....

Thanks

[Lawrence Coppari]

My tranny does not wiggle. I would have noticed when I change the oil in it because the plugs are hard to break loose. Tranny would have moved then.

[Ebs]

Is there strange any noise when this happens s-man?

[s-man]

No noises whatsoever. Just whent for a nice cruise tonight, easy going right throught the tach range very smooth to redline, matt it and it feels as if a tire is coming off..

I am pretty sure its a tranny mount.

Remember this, if the tranny mout is worn or torn, this will not only cause the rear to chatter, but it will also put more duty on the engine mounts.

thanks ,

86 951
91 nsx
72 240z
73 911 "S"
87 928 "S-4"
88 M-5
00 Boxster "S"

[Ebs]

I was wondering if your problem is similar to mine, as I have a bad noise under load from the rear of the car. I worry my diff/gearbox is in trouble. Good luck with your problem.

[1.2gees]

Tranny mount being a bit loose to "wiggle" is ok. Your problem sounds like loose tolerances in the CV joints, probably the passanger side, but check both.
Ahmet

[1.2gees]

"Remember this, if the tranny mout is worn or torn, this will not only cause the rear to chatter, but it will also put more duty on the engine mounts"

The transaxle only hangs from it's mount, so a worn transmission mount would only (possibly) relieve stress from the engine mounts in the fore/aft direction. I don't think motor mounts are made to be more sensitive to torque in certain diretions so I wouldn't worry about this.

Noise from the rear could be internal to the transaxle, but again the CV joints should be the first things to check.
Ahmet