I had originally posted this under someone else’s post, but am reposting with a more descriptive title...I have a drivetrain vibration in my 190D 2.5 Turbo. It had originally been an automatic transmission car and I did the 5 speed manual conversion about five years ago- it was a professional installation by a trusted shop. (All the parts for the conversion came from a single donor car- a 1992 190E 2.6 Sportline) I drove the donor car very briefly for a few miles before dismantling it but didn’t notice any particular vibration with the drivetrain in the donor car.

In my 190D 2.5 Turbo, there had been no vibration prior to the trans swap, and aside from this one problem, it was a flawless and perfect conversion. After installing the donor 5 speed, drive shafts and 3.27 diff into my car (but retained my original axle half shafts and cv joints)- I started noticing a rotational vibration/“thumping” at a rate proportionately increasing with speed- generally over 40 mph and continuing to over 90. I have tried different sets of factory wheels- 15 and 16”, and different sets of tires which have been rebalanced several times...the same vibration remains- it’s not the tires or wheels.

The vibration follows the drivetrain speed, not engine speed/rpm. If I’m traveling at any speed and push the clutch in and take it out of gear, the vibration continues at the same frequency regardless of engine rpm. The only other slightly strange noise I notice is if I’m backing down a sloped driveway, I get a funny “whrr, whrr, whrr, whrr” noise if the car is out of gear and I’m rolling down without using engine power. If I use reverse gear under engine power to reverse, I don’t get the sound.

I’ve checked the driveshaft halves, and the alignment marks are properly aligned. I also have replaced both flex disks, center driveshaft support and bearing, front shaft vibration damper, clutch, pressure plate, flywheel, engine and transmission mounts, shifter bushings, etc.

From what I’ve read, about the only other things that are left that could be wrong are:
- Driveshaft itself is out of balance. I can’t imagine this is true as the factory weights are still attached and there is absolutely no visible damage.
- Driveshaft u-joint wear causing an imbalance- I have never experienced this before but I suppose it’s possible...my 190D and the donor 190E each had a little over 150k miles at the time of conversion...
- Rear transmission bearing or a differential bearing- I have also never experienced problems with either of these before but I have read that others have...
As for all the above parts I have replaced, they were all factory Mercedes parts bought from the Mercedes Classic Center.

Any and all help would be appreciated. This vibration annoyance is the only thing that keeps this car from being an absolutely perfect driving experience!

J.G.