eta dual mass clutch vibration question

[guardodoc]

Oct 1986 325e

I get a vibration at 70-80 mph worsening.
It persists when clutch is depressed.
It occurs even when wheels off the ground (on a lift).

I've replaced driveshaft. CSB, rear wheel bearings.
& rear tires new & balanced

Question. Is there a part of the driveline in the transmission that
spins when clutch is depressed, but wheels are turning that could be out of balance ?

My next step is to replace my 2.92 open diff. with an lsd.
But wonder if something spinning in the transmission is out of balance.

Apologize in advance for my stupidity as I'm not a car guy

[jlevie]

If the vibration is present when the clutch is depressed the cause will be from the drive shaft back. Since the vibration occurs when the car is on a lift, remove the rear wheels to eliminate them as suspects. If the vibration is still present it will most like be from the drive shaft. The halves may not be correctly aligned. or if a used drive shaft it may be bad.

[guardodoc]

Thanks

Thanks. So you don't think it could be the diff ?

[jlevie]

Thanks. So you don't think it could be the diff ?

The differential is unlikely to be the cause, but anything is possible. You should be able to prove or eliminate the differential with the car on a lift. When the drive shaft is bad you can frequently see a bit of motion at the CSB when the vibration occurs.

[guardodoc]

Thanks

Thanks. Will give it a try.