Hi all,
I've been trying to fix a vibration in my 84 500SEL for quite some time now. The vibration is first felt at about 20 mpg. It is just barely detectable. At about 40 mph it gets a little more pronounced. and then at 75 to85 mph it is bad. So far the the driveshaft has been replaced (used one from an 89 420SEL). the rubber flex joints (new), center support bearing and carrier(new) with no change. I was really shocked there was no change since the carier bearing and rubber suport were shot and the flex disk were full of cracks. Of course the tires hav been balanced on more than one ocasion and rotated more than ounce with no change. I finally got serious about this and set the car on jack stands(actually on a lift with jack stands under the lower rear supension arms) and ran the car at 20 mph and could feel the vibration. Then at 40 mph and again could feel it, and then at 80 and it was bad. It felt the same as going down the road. Removed the rear wheels and rotors and got the same vibrations at the same speed. Tried running it to about 90 mph and bumped it into netural and it had the vibration at 80, 40, and 20 mph as it was slowing down. I have come to the conclusion that it is one of the axle shafts but can't tell which one it is.

Any one have any ideas what else I could do. I can't take out one axle for several reasions.

Thanks for any help.

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84 500 SEL (307,xxx miles)