Okay, I have read a lot of vibration posts, but can't seem to find what I am looking for.

This new to me 300 wagon has a vibration that starts up at about 55 mph and stays thru 75. I would guess that it is at it's worst at 65. I also noticed a pronounced vibration while accelerating up an incline - say 25 mph.

The vibration started after I changed out the motor mounts. The old mounts were really bad. At the time I figured the new mounts shifted the engine angle and cuased the bad center support to start complaining. I just finished changing the center support and flex disks. The vibration persists. The transmission mount is intact, but not hard. The U-joints felt okay. Everything was marked and reassembled in line. The only thing that I did not do was roll the vehcle befor tightening the shafts.

I do have a torn boot on the driver side half shaft. Can a dry joint cause this type of vibration? The harnomic balancer is tight. The tires are basically new.

Any thoughts?

Thank you

I cannot think of any reason jacking the Engine up and checking the Motor Mounts would cause a problem except that it could stress the Transmission Mount.

New Transmission Mounts do not cost much. It could be wasted money, time and effort to change it but at least you would know that it is not causing the problem when you are done.

You ought to try loosening the Coupling Nut and rocking the Car back an forth and tighten it again. It does not cost anything to do that.

I know that on my Car when I pulled the shaft end that had the U-joint I could hold it in my hand and the U-joint would not flex on its own weight.

I am not sure what problems a stiff U-joint can casue or in your case possibley 2 stiff ones.

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84 300D, 82 Volvo 244Gl Diesel

My thought is vibration due to tranny mount. If it is spongy and soft feeling, replace it. That's where your wiggle is coming from.

The Benz drive shafts seem to be sprung to self-centering. My mechanic notice this "weirdness" when changing out the center support bearing. The shaft doesn't hold a kink, it'll straighten itself out on the bench.

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Cheers!
Scott McPhee

1987 300D

I have owned my '85 300D for 20 years and have had vibration crop up several times.

- My first guess would be that you need the tranny mount. This as you know is part of a 3-point engine support. Installing only the engine mounts causes the front of the engine to be cocked up at an angle. This may require the front flex joint to handle too big an angle. I had a similar problem when shop once had my engine out. They fixed it so I don't know details.

- On another occasion, it was the driveshaft support bearing. But you had the problem before you replaced that, so unlikely the cause of the problem.

- Flex joints - after installing tranny mount, maybe re-check installation is good (proper torque etc)

- On one occasion, vibration ended up being a rear caliper binding. Changed calipers and freed up hand brake and vibration disappeared.

- Tires - I once had terrible vibration on rough surfaces with brand new tires. Had an alignment and that helped. Eventually as tires wore in, vibration went away. Also once had balance weight fall off causing bad vibration.

Good luck with it. You have already done a lot of work - hope you get it sorted out!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Well, no dice. Just changed out the transmission mount and the vibration is still there. I did notice that the tire pressure was way high - 65 ish. Don't know who would do that, but I have reduced the pressure to 30. Strange.

I am going to loosen the shaft nut and roll the car as suggested.

Any other thoughts would be great.

A dynamo test might help diagnose the location of the vibration...

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Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)

New tires...high pressure...just thinking...could it be simply a tire or two out of balance? I remember having a really bad vibration on my Ford Explorer at 68 mph that was cured by rebalancing the tires.

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1976 240D "Katja"

If you have a dry half-shaft, that's where I would start. You're going to have to replace it anyway, so you might as well do it first.