Hi,

I see from doing a number of seaches on vibration that there are many, many posts relating to vibration, and successful diagnosis and repair is very difficult..

My car has a vibration or thrumming, drumming noise starting at about 120 km/hr and up, not heavy, but very noticeable and annoying. It sounds that it is a higher frequency than from the wheels or axle shafts.

I had the driveshaft balanced, new centre support bearing and mount, and driveshaft bushings done but no difference. The flex disks were apparently OK.

I would think the possible causes could include:
1. driveshaft bent or unbalanced (already balanced)
2. flex disks damaged
3. U-joint wear
4. worn centre support bearing or rubber mount (replaced)
5. driveshaft angular misalignment (transmission/front shaft ;front shaft/rear shaft; rear shaft/differential)
6. loose or worn differential mounts

Does anyone have any advice on how to narrow down the possible causes? Does anyone have a copy of the MB TSB on driveline vibrations that recommends addition of a damper on the differential? Do you have a copy you could send me?

I was thinking of tape recording the sound inside the car and putting it on an oscilloscope to look at the relative frequencies. One can easily calculate the driveshaft RPM vs road speed, but there may be other multiples as well, eg: 2x per rev, 3x per rev, 6x rev, based on physical geometry of flex disks and fastenings.

Advice on diagnosis and most likely causes and fixes would be greatly appreciated..

Very best regards,

James
Toronto, Canada

Wow,,,, sounds like you have things pretty well covered, but still have the problem. All I can tell you is we had the same type of vibration in a 126. After all other possibilities were checked, I did a search on this site. I came up with a possibility of shiming the center driveshaft support a bit. I put a little over 1/8th shim under the support. That positively took care of the vibration. Hope this helps.

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95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K

Thanks Pete. Did your shims lower or raise the driveshaft relative to the car? Did you check driveshaft angular alignment first?

Regards,

James

I would not exclude the wheels/tires until I had them exchanged with a different set.
Bruno

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1992 300TE 160 kmiles

After very similar troubleshooting and frustration. I did a runout check on the front rortors and found that my LF Hub had become warped. I dont know how or why. My only explanation for the vibration is. The rack and pinion stearing section is mounted to the frame directly below the engine mounts. The engine mounts are fluid filled for dampening. It seems any brake or wheel vibration caused a transfered oscillation into the fluid filled engine mounts and passed back threw the drive line. They work great for engine Vibs but not transference.
I bought an OE Hub from carquest assembeled and ready to install, bearings installed even had MB green grease in them. The vibration is gone smooth as glass especially at the 53-62 mph trouble speeds. This problem really didnt effect the car or gas mileage. I could never feel anything in the brake pedal or steering wheel. It drove me crazy. Finally got it, not to mention flex discs, brembo rotors, drive shaft support and a cv axle and new tires. Good luck hope this helps ya. I been down your path and it gets long.

This may seem like out in left field, but I had a similar thumping sound that increased with vehicle speed. Changed flex discs, but thumping still there. It was the inner sidewall of the rear tires that was coming apart. Outer sidewalls looked perfect, but for some reason the inner sidewalls were bad. Perhaps its worth a check.

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ARVY

1999 E430
1999 C230 Kompressor
1992 300E (write-off)
1984 190D 2.2 (sold)

James, I recommend that you check the tires too. Easiest way is to swap a complete set of known good wheels/tires to see if the vibration/drumming goes away.

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Fred Hoelzle