280SE 4.5 Driveline Vibration - Still hunting for it

[Bezant]

Hi guys,


Two big symptoms I am having a hell of a time tracking down. A rough shake coming up through 25mph, and a vibration in the 70mph range. Vibration is felt strongly in the seat and body of the car not the steering wheel.



Have done all the following:

• New tires and double checked the balance
• Shaft balanced at shop
• New u-joints staked in
• New flex disc
• New carrier bearing
• New carrier bearing rubber donut
• Car rolled out properly on a drive-on lift before tightening the spline nut and center bearing housing bolts
• New differential mount

I found a thread from '06 where Arthur Dalton said the trans output flange could get lose, but I'm not sure how to check it or what tools I would need to tighten it and all the links are dead in the thread. Other than that I have no idea, driveshaft place suggested it could be an issue in the differential or rear axle.

[97 SL320]

What is the history of this car and how did the symptoms progress?

Vibration from 0 to 25 is usually a drive shaft issue because it spins 3x ish of wheel speed. There just isn't enough force from a wheel to cause vibration at low speed. ( unless the tires are dramatically out of round . )

I'd put a dial indicator on the drive shaft just to be sure something isn't off center.

Does this car have a swing real axle ( low center pivot point ) or CV axles like a front drive car? I've seen inner joints wear to the point the axle shaft spins off center of the joint housing.

[Bezant]

As far as I remember it's been doing it since I got the car.

To be clear the vibe isn't 0-25, it's specifically right as I accelerate through 25.

W108s are swing axles.

[Sugar Bear]

Arthur Dalton may respond to a PM or e-mail. For the high frequency vibration, check the pinion angle, it caused a vibration in my W124 that was hard to find.

Can anyone comment on how the angle can be adjusted on a 108? 124's are easily done with shims at the front topside of the diff.

Good luck!!!

[Idle]

This goes way back.....

A similar vibration was vexing a friend of mine about 30 years ago. He went through everything and finally replaced a U-joint sort of thing in the axle. It was connected to the differential hub and also to the part of the rear end assembly that swings. I have not been under a 108 for some time but I think this would be the left axle.

The U-joint thingy allows the swing axle to, well, swing. The motion of the right side axle is controlled by the big crosswise spring or hydroshock (if it is still there and has not been replaced with a spring).

But don't tear your axle apart just yet. Others might weigh in on this since tearing into that part is a very big deal. And like I said: This was 30 years ago. Hopefully I am wrong about this.

A random thought: Is the part of the floor where the carrier bearing bolts to sound? A little rust here could allow some flex even if the bearing is bolted in like it should be.

[Bezant]

Hi, yes all the floors are solid.

I too am fearful it will come down to extensive rear axle/diff work