Chasing a vibration. Help !

[guardodoc]

I've got a 1986 325e all stock.
Vibration occurs above 60mph, worse with acceleration.
Definitely a vibration, not a shake or shimmy.
Not engine speed related.
Occurs also with car on lift and only rear wheels spinning.
Occurs when clutch is depressed and coasting.
Replaced driveshaft, flex disc, CSB, motor mounts, trans mounts, rear wheel bearings,
Could it be the differential ?
or something in transmission that still spins when the clutch pedal is in ?
Sorry in advance, I've got almost no mechanical experience.

[jlevie]

Was the replacement drive shaft a rebuilt, or used part? The symptoms are suggestive of binding u-joints in the drive shaft, which could be the case with a used drive shaft.

[guardodoc]

driveshaft

It was a remanufactured and balanced driveshaft from Powertrain Industries in Garden Grove. That didn't cure the vibration. I thought it was the engine until I noticed that it doesn't change with engine RPM, just with speed. So then I had flex joint, CSB, motor and transmission mounts changed.

[e30leigh]

did you change the hanger bearing? that is straight where i would go with those symptoms. also was the hanger preloaded? they need around 1/4 inch preload. possibly slightly more if itll go easy.

[guardodoc]

e30 leigh

I don't know what a hanger bearing is. I did replace the center support bearing
with BMW oem.

[e30leigh]

sorry. centre support bearing, hanger bearing. same thing, different name. just what we call it here on the bottom of the planet.

did you preload it? its possible it might need to be preloaded. in my experiance, mainly with e36, 46, 34, 39, 60, 65 they all need to be. id say it would be the same with the e30's looking at my manual one on the floor of my garage.

[E30Gus]

Are your tires balanced, true? how do the half shafts feel?

[guardodoc]

half shafts

How do I check them ?

[_r2h]

Grab a hold and give them a good shake.

[guardodoc]

half shafts

With the wheels ofof the ground ? Sorry for the basic questions.
I'm new to half shafts.