I have had a persistent clunk coming from the rear end and I have narrowed it down a little, but need some help. I put the car in neutral and tried to turn the driveshaft by hand - very little movement, couple of degrees of turn back and forth.

The clunk is very clearly coming from where the driveshaft connects to the differential. Very noticeable when I push the car forward and let it rock back - with the car in park, of course. When I push the car, the driveshaft turns a little in both directions, depending on if the car is rocking forward or back, and clunks.

It is not coming from the mounts, or the sway bar links, etc. and the flex disks and the center bearing and mount have all been replaced within the past couple of years - and they still 'look' good. I checked the fluid in the differential and there wasn't any! At least, not that I could see or feel with my finger. I added around 1/2 quart, and I'm afraid that it has been low for years - I have had the car since 2003 and have never checked the fluid level in the differential. I know, I know... I haven't driven the car all that much either, but...

Any ideas, or suggestions?

ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

I would tend to lean toward a bad bearing in the differential, perhaps the bearing on the input where the driveshaft connects. Some bearings wear until they are very loose.

You may be able to get closer to the problem if you jack up one wheel so that you can turn the axles and thus the differential and driveshaft. Then you can move things back and forth to help locate the noise.

Going without enough gear oil can wear out a differential early - so you may be looking at a rebuild or replacement. They should be fairly easy to come by as most of the time they never go bad in the life of most cars, so a used differential may be cheaper than trying to find someone who can actually rebuild a MB differential.

But that's getting ahead of the issue - you could also have a clunky axle.

So when you jack up one side and get down on the ground to listen, I think you will have more clues.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles