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.

when you installed the new driveshaft did you check if the u-joint is notchy in a straight position? if yes then you need a driveshaft rebuild.

I had to have my driveshaft shipped out for a rebuilt on my 300SE because of a notchy u joint (only had 120k at the time)

another possibility is that a transmission mount height is different between automatic and a manual. It would be a good idea to put a digital protractor on your transmission/driveshaft/diff to check that everything is straight vertically and horizontally

I didn’t check for notchiness in the u joint...at this point I may take it down and check. I did swap out the auto trans mount for the correct 5 spd version so that should be ok.

Any recommendations on a good MB driveshaft rebuild shop? I’m in eastern PA but will ship to wherever there is a good reputable place...

J.G.

Still checking with a protractor is not a bad idea when doing swaps.

I used those guys: https://www.wholesaleimportparts.com/

Give them a call first

Total was ~$380 all in

They paid for a shipping label to texas and once they got it then in 1 day they replaced the u-joint, bushings at each end, center bearing and support, balanced the driveshaft by removing old weights and putting new ones on and painted the whole thing and paid for shipping it back to me.

I've also now noticed that occasionally the vibration level varies...sometimes it's quite light and then seems to get stronger. Also, I've noticed a different level of vibration while at high speed while turning or changing lanes. I'm starting to lean towards either a wheel bearing or a differential bearing given the change in vibration level coincident with side/lateral movement??...

J.G.