Strange Driveline Vibrations - PeachParts Mercedes-Benz Forum

Boardmonger · #1 08-13-2007, 02:14 PM

Ok, this is the 79 300d euro 4 speed. The car was driving fine about a month ago, then came a funny vibration when starting off. Dropping the cluth (well not dropping, but quick engagement) makes for smoother takeoff, whereas a slow engagement provides a driveline vibration. There is the same case for downshifting, but this is only noticable during start-1, 1-2, and downshifting all gears. There are vibrations engaging reverse, but they are not as noticable.

Our mechanic looked at the car and he ruled out the clutch, stating it was engaging properly and did not act like a worn out clutch. In inspecting the driveline, he found the motor dampners where shot and replaced them, but that had little effect. He then determined the driveshaft was worn, with the U-joint excercising limited rotation. He stated the joint should be able to rotate freely and not "lock" in any position, but ours was locking when straight. The entire shaft must be replaced to cure this symptom because the is no place to lubricate and you cannot replace only the joint.

So he sent us to pick and pull and we pulled two shafts, both with similar (but not as bad) locking symptoms as ours. In replacing it, there was little effect on the vibrations.

So that is where we are at. I still think we may be having clutch problems, maybe a worn disk or something, but I am not sure. Has anyone experienced anything like this? My mechanic, a mercedes factory trained technician for the past 35+ years generally knows his stuff, but is he correct about the driveshaft? I have never heard anything like this, so I thought it was strange. Any ideas on the subject are greatly appreciated, I would hate for it to be a cluth problem.

And note, the vibrations are from up front, so it is not any rearend issues, so that kind of narrows down the possibilities, well at least I hope so.

rrgrassi · #2 08-13-2007, 02:18 PM

How are the flex disks and center support bearing? Also what about pressure plate and throwout bearing?

JackG · #3 08-13-2007, 02:24 PM

Quote:

Originally Posted by rrgrassi

How are the flex disks and center support bearing?

Ditto

Boardmonger · #4 08-13-2007, 02:25 PM

Flex disks are good, center support bearing is in ok shape, but I will probably replace it soon.

I am not sure on the condition of the throwout or pressure plate.

Boardmonger · #5 08-13-2007, 04:24 PM

Any other ideas?

bigblue · #6 08-13-2007, 04:37 PM

If your mechanic is good he probably would have considered/ruled out this one but it sounds to me like a it could be a warped flywheel and/or pressure plate since it holds well and you don't experience much of the vibe when releasing the clutch quickly.

If you rev up the engine and slowly release the clutch to launch do you still feel it?

winmutt · #7 08-13-2007, 05:05 PM

I vote for flexdisks, center bearing and more than likely warped flywheel, clutch etc.

Boardmonger · #8 08-13-2007, 07:25 PM

Is a warped flywheels common? How would that even happen?

yellowbenz · #9 08-13-2007, 08:01 PM

My 240D has similar symptoms. I find that if I increase the revs the driveline clunk is absent. With lower revs from a start it bucks. Downshifts and shifting at speed is normal. I think it's the driveline support bearing on my car thats trying to fail. I hope to have time to crawl under the car this weekend when temperatures will hopefully be less life threatening.

Kevin
1979 240D manual