MY 1995 E300 with ASD differential and 94K miles was noticeably loud when I bought it 1K miles ago, but I bought it anyway. I owned one before, and my father owns one now, so I have comparisons to what it should sound like, i.e., no noise at all! I changed the diff fluid, and bled the hydraulic fluid, and even added Lucas Oil Stabilizer, but no change in sound.

It is a vibrating medium low pitched cyclic “wha wha wha” sound from about 15 mph to 60 mph. It is not a grinding metal or whining bearing noise. It is noticeable on acceleration and deceleration, and slightly less so when coasting in neutral. It is not the flex disks or center support bearing.

There are no records, but the differential end cover was opened before me (the sealing compound over applied around the end cover is obvious). The MB-trained mechanic I use suggested the pinion nut was torqued too tight from that prior work, so he loosened it slightly, and no change in the noise level. If it was torqued too tight from repairing the seals let’s guess, then the spacer bushing has been crushed, and needs to be replaced, which means rebuilding the diff.

So, rebuild this differential (replace spacer bushing and washer, seals, maybe drive pinion and crown wheel if damaged), or find a used one. I know the ASD does work, as I tested it in snow last winter! Since this is an ASD unit, they are hard to find.

I’m going to search for a used diff (thanks Dave M for some leads), and appreciate other leads and thoughts.

Dave

Just make sure that you used the special MB diff fluid for limited slip differentials.

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Dump the Lucas stuff/It can cause foaming leading to the noise.

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