Rear end noise

[kchemers]

89 300TE 150,000 miles I am getting a whinning noise from the rear end. I just had the rear bearings replaced. Between 70 and 80 mph a loud whinning noise can be heard, no other time is it noticable, reading the posts some one said its the rear diff gears, are they wearing out? is it dangerous to drive? is this a major repair? diff lube was changed at 140,000 it didnt look any different than the fluid I put in
Thanks

[crhenkel]

I doubt anything anyone did created the whine, it is common in the W201 and W124 car diffs, they are the same basically. They will typically wear at a certain spot in the gears that creates a whine at some speeds and not at others. Common problem, only fixed with new ring gear set, expensive. M.B.DOC on the forum rebuilds diffs for a fair price. Contact him, he is on the forum as a moderator all the time. He is in Georgia and a diff ships very nicely in a 5 gal plastic bucket.
There is not so much a "problem" with the gears as there is a wear pattern in the surface of them from use. It is common. It is still safe to drive, just annoying when you are traveling at the speed the diff whines at. It creates a whine at certain speeds and not others. If you can make the whine come and go by speeding up and slowing down you have "gear whine" and bearings wont fix it. The bearings may even be just fine. The only way to rid a diff of the whine is new gears and they are so expensive it is not worth it. Talk to MB DOC. he can tell you the low down on the rear diff issues.
Good luck.
One thing to do for the whine is use a heavy gear oil and place sound proofing and or an old blanket under the rear seat assembly, To mask the sound. A good heavy gear oil is fine for the diff and helps cover the whine.
I had a used limited slip rear diff completely rebuilt with bearings and friction plates and washers and it still has a small whine, better then my original diff, but still there. The parts alone cost over $200 for bearings, cups, plates, washers, seals, etc and I did not buy all OEM MB parts. MB parts would have been 2 or 3X more expensive. Still did not buy gears, they cost $850, I would have had $1000 in parts and $500-$600 in labor.
Good luck

[kchemers]

I love this site. Thanks for the info, I'll try a heavier lube

[t walgamuth]

The wagons give a lot more road noise since everything is right below the passenger compartment....not like a sedan where the back is under the trunk.

Tom W

[kchemers]

How heavy of a lube can I use????????????

[crhenkel]

Mobil 1 synthetic has two weights, the typical 75w95 I think and then a heavier, I used it and it was helpful in reducing the noise. I used the synthetic Mobil1 since the diff had no leaks at all and they had a heavier weight, got it at Autozone. Worked good.