This post is for those of you who drive an old mercedes that has a slight to moderate, rythmic vibration in the drivetrain (that tends to be worse when power applied).

For six months I tried to fix a vibration in my 300CD (138k miles). Replaced many parts (motor/transmission/rear end mounts, rebuilt and balanced main driveshaft, new center bearing, new flex discs, repacked front wheel bearings). None of this solved problem. Finally I replaced half-axles with rebuilt units from Fast Lane ($200 each with exchange). Vibration now gone.

Message is check out the half-shafts. My car has been carefully driven and maintained so my guess is many other older mercedes need these axles replaced. Makes driving at speed so much more pleasant.

Nic in SC

Vibration in rear end
 

I have an 1982 300 D. I am having a similar problem. Slowing down from crusing speed at appox. 20 mph I have a "rattle" that appears to come from the differential. Also on acceleration if I hold at about 30 mph I have the same sensation. As I accelerate the rattle or vibration tends to fade away.

It's driving me nuts ! I have had it in the shop three times and nothing can be found. Is this similar to you situation? It may me an answer to quite my ride.

R. Tucker
1982 300 D 91,000

I had a similar problem with my 87 300 sdl. I had it to 2 shops, one an independent that thought it was the driveshaft, and the dealer, who....thought is was everything and started replacing things...to no avail.

My problem turned out to be a bad left side half shaft. You could grab it and move it back and forth.

Drive trains are difficult to troubleshoot. It could be the shaft itself out of balance (if someone worked on the shaft before), the center carrier bearing, the flex disks, half shafts, and even the rearend.

Make sure you don't have a wheel out of balance. Drive train problems are usually found when under power, so if you coast and have it, it probably a wheel.

My problem would only occur at 75MPH plus. That makes it difficult to troubleshoot for a dealer in the suburbs. It's rather dangerous to put it on the rack and run the drive train up to speed.

After all that worthless chat, I would try to pull and tug on each half shaft and see if you notice any different between them.

If one is loose, I would order one from the MB salvage yards on the net...used ones are a lot cheaper, and "swap it out".

Joe

Richard,

I think Joe's right, troubleshooting a drive train problem is hard. Could be anything. I had to "renew" most everything in my drivetrain before solving my vibration completely. Wasn't any one item. I think these old diesel Benz's just want to vibrate and to get really smooth ride, you have to take a comprehensive approach. Worth the effort though - mine now rides great.

I personally wouldn't buy a used half shaft. Rebuilt ones from FastLane are $200 and you can spend as little as $129 at local Advance Auto.

Here's my path to smooth ride:

- new motor mounts/transmission mount
- new center bearing and flex discs on drive shaft
- balance drive shaft and rebuild universal joint
- new differential mount
- rebuilt half shafts

Total cost approx $1,200 using local indie shop. DIY'ers can save a lot

Nic
'85 300CD @138K

My '79 300SD has developed a "duh-duh-duh-duh-duh-duh..." when I go up a hill or when I hit exactly 37 MPH. It is getting worse, and I have not ventured under the car yet. I am hoping for it to be a flex disc, or center bearing. I would think an axle shaft would be noisy all of the time? I will report back on my findings.

Thanks for all of your help. I now have several suggestions to pose to the service techs.

update
 

I recently took my vehicle to a great local shop. As several of you thought it might be, it seems to be the left half shaft. Going into the shop this week for a full analysis , but definitely the left half shaft to be replaced. Thanks for all the advice. I'll let you know how it goes.

Repairs completed
 

As NIC thought, it was the half shafts. I had them replaced and it drives like a new car ! Thanks for all the help.

I found a half-shaft at a local salvage yard for $75, and replaced it myself this past weekend. The old one had a missing boot, and was way overdue to be swapped.

As mentioned in this thread, the difference is very pleasing. Before, when traveling at 60mph plus, images in my rear view mirror were fuzzy and "out of focus." After replacing the shaft (about a three hour job), the ride is much smoother, and the mirror no longer vibrates.

I'm sure it's hit and miss with these junk parts, but I guess I lucked out. Now to replace the other side...