Vibration in rear of car - running out of ideas

[Derek A.]

I have read a lot of previous posts about seat-of-the-pants vibration - without seeing a whole lot of resolution.

From 45-65 mph I have a vibration. I can see the passenger seat moving, I can feel it in the seat of my pants. There is no shimmy in the wheel. At 85 mph the car is smooth as silk. Applying the brakes does not make a difference.

The following has been done.

1. Drive shaft replaced w/new center bearing
2. New trans mounts
3. Balanced rear tires then swapped out rear tires - no change
4. Rebuilt both rear calipers - driver side was sticky.
5. Ran car on hoist - no obvious shakes.

I have no noises or other problems. Cars drives great. I just have this wicked vibration. Any ideas on what else to pursue?

Derek.-

[rob101]

could be the dog bones (rear pittman arms thats the only idea in my mind.

[Derek A.]

Dogbones were replaced last year - they are in good shape.
Rear subframe bushings year before.

[Zeuk in Oz]

When were your thrust arm bushings last changed ?

[Kobe Diesel]

Check the CV joints on the drive shafts? if the rubber boots are worn and all the grease has flung out, well the joint is shot, and this can give you vibration.

It's a long shot but also check the differential mount.

[wingman]

What do your tyres look like? Are they balanced and are your wheels completely round? Sounds silly but usually the most basic things are overlooked.

[Derek A.]

I would think a thrust arm problem would manifest itself in the front end? I had 750 bushings put in a couple years ago.

I thought about the rear cv joints. The boots are all intact.

I swapped out different wheels and tires - and it didn't change. So its not a wheel tire issue.

The only possible caviat to the whole thing is that I have concentrated efforts on the rear as the steering wheel is rock solid. I can't imagine that it would be a problem in the front.

[stargazer_61]

Have you checked your rear control arm bushings? While diagnosing my vibration issue, the ones on the left side appeared cracked on my 540i.

[Derek A.]

We ran the car on the hoist and nothing jumped out. So its possible its a control arm issue. But it doesn't happen all the time and varies in its degree. I was really thinking wheel and tire - but I swapped out wheels/tires and it didn't make a different.

Generally with a bushing failure - I would thing that there would be a pull or a clunking noise.

[632 Regal]

out of round tires. I dont care that you swapped them out, probably have another set of out of roundies.