I have a 1989 420 SEL ,vibration that comes and goes, had all tires balanced no bent rims, no bad tires,new shocks,new front struts,tie rod assy. rebuilt steering box, vibration is not speed or RPM sensitive (really noticable at or above 70 MPH), seems to be thru the center of the car, feel in steering and seat at same time, thats why I say center related. Thought it may be AC clutch related, but turned off and on did not make any diff. Called the dealer cann't seem to help. Checled u-joints,flex plate rear end pinion bearing for play found everything OK. ANY SUGGESTIONS????
All help would be very much appreciated.
Thanks for your help
Tim
PS 128K miles.

I suspect it could be your drive shaft ...

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.

Do you have any vibrations in the steering wheel when you are applying the brakes? As if the rotors are uneven or warped?

I had the exact problem you describe and the problem turned out to be in the front rotors. I had some pulsing when braking but I never thought that a rotor problem would cause vibration when the brakes were not being used. It was not until I turned the rotors that the vibration while driving went away. I cant explain why or how the warped rotors is causes the chassis vibration, but it was.

If you dont have any brake pulsing, then I am clueless.

Let me know what you find if you ever get it cured.

__________________
I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

Checked drive shaft, thought might have lost balance weight, every thing OK. I had the dealer do the brakes, this vibration only occoures while drivung nothig while stopping. I have checked all things I know of, next thing is to go to dealer. It's strange,it has me puzzeled. Thought maybe some one there could come up with some thing in regards to center line vibration, thought it could be the vibration damper NOT.
Tim

SAME problems with 190e

I JUST had my 190e in the shop for the same problem, and they found a problem with the idler arm and the wheel bearings. They had to fix both of those, and thus far, no more vibration. I'm not sure if your car has these parts or not, but thought I would post in case!

Good luck,
Michael.

Inspect all the engine mounts and transmission mounts and the small shock on the engine mount. Also check exhaust system hangers.

Sounds like a motor mount to me. CAREFULLY jack up the motor slightly and look for separation or deterioration.Regards

When all else check out fine and still no solution, try checking your shocks. Yes, I did say shocks. Mine was causing vibration on speed past 70mph and I could feel it in my teeth when it did. Replaced the shocks and the problem went away.

My car has the same problem, but I am going with bfl's answer from another post. Also, mine does it more when braking into a right turn, weight being mainly on the drivers side. Consensus is a front susp ball joint. I am having it checked out tomorrow and will let you know. PS. do a search on "soccer." You should find a relevant post answering your problem.

what about checking the diff mounts? Heard they can cause similar symptoms to yours.

I expect the problem is wheel balance and/or motor mount related.

I know you said the wheels have been rebalanced, but it is extremely common for them to use weights only on the inboard edge of the wheel. This is called static balancing and will NOT correct vibrartion, it only keeps the wheel from bouncing up and down. If you balance the wheels on a properly working computer balancer on both planes(inboard and outboard) you will keep the wheel from "wobbling." This is an extremely common problem because there are many tire stores that think that they only need to static balance wheels. I got so tired of fighting with them that I bought my own Coats 1001 computer balancer. Every car I have can now be driven at its top speed with ZERO vibration.

To the motor mounts, when one goes bad it will make you think you're in a B17.

Good luck,