Hey I have got an 1985 300 D turbo diesel. This car runs like a champ. Oly has 165,000 miles on it. But there is just one problem; starting at around 40 mph the car goes in kind of an up down movement. I had got the wheels balanced and the shake was still there. Everything is tight under the car. What else could it be?

 

trust you talk about w124/w201
did not catch what is up&down movement cause it's probably your front shock absorbers need 2b replaced
if it just a vibration-check rear final drives&rear suspension
if you feel a vibration on your steering wheel-check steering wheel shock absorber (later model) AKA pendulum lever that is a part of steering mechanism- not sure how to translate same in english

 

Since you mentioned wheel balancing I assume the "shake" is like the wheels were out of balance. Smart, ain't I?

If the wheels are in balance and your car still "shakes" at a certain speed as if the wheels were out of balance, the wheels and tires may need to be indexed.

Wheels and tires aren't perfectly round. When a tire is mounted on a wheel such that the highest point of the tire is on top of the highest point of the wheel, the two high points become exaggerated to the point that it can cause a shake.

During indexing, the tire is mounted such that the high points of the wheel and tire are opposed. This cancels out the high points and makes the wheel/tire combo more round.

 

highest point of рoint wheel/tyre- pls explain what do you meant by that. how you can find highest point on round surface?

 

It's easy. I take the car to a tire store like Goodyear or Firestone and tell them to index the wheels and tires. I sit in the waiting room and drink coffee or soda. I pay them when they're done.

Okay. But you're from Moscow. I doubt if there's a Goodyear or Firestone store on any of the corners there. I don't know what to tell you other than it's done here routinely. I've never gone into the shop area to watch it done. I would think they use a dial indicator of some kind and hand-spin the wheel and tire separately, mark the high points with chalk, then mount the tire such that the high points oppose each other. I believe race car teams also index or otherwise deal with high points and roundness and stuff. Sorry I can't be more specific.

If you really want to know, you can call the last store that did the ones on my SL. They'll be glad to explain how they do it above what I've told you. It's called United Tire and Alignment and their phone number is 770 889 2700. It's in the Atlanta, Georgia area. You can probably find info on the Net as well. I haven't Googled this at all.

 

Have someone take a look at the carrier bearing in the center of the driveshaft. I had that problem and the car would shake untill the driveshaft found it's rotational center. Mine shake happened at about 30 MPH.