I'm chasing a problem with a 93 190E 2.6 that's really tricky. It's kind of something you have to wait until it gets worse to figure out but at that point it may be too late. In the morning when first moving off I get a clunk in the rear as I step on the accelerator pedal. After that, normal behavior throughout the day. Hasn't gotten worse so I live with it. I have been told it's a sloppy diff but I'm skeptical. They aren't supposed to get that sloppy until after 200k, but there is a lot of slop somewhere back there that I'd like to tighten up. This car is kind of a cream puff and hasn't seen much abuse, but my stepmother drove it some lol so I don't really know. She may be one of those people that doesn't wait until the car stops moving to bang it into drive when backing up. I can feel this slop when letting of the pedal under engine braking. Had it up on the lift, independent Mercedes mechanic has inspected it, couldn't find anything. I've looked underneath there myself a hundred times and nothing seems bad. Got one moist axle. Just put some Redline Shockproof Heavy in the differential but no real change. Could it really be inside the differential, where the big pin locks into the center carrier? Could that hole in the carrier be elongated to the point where I get that slop? I've never heard of anyone replacing a differential in one of these that wasn't used. Kinda would want a new one or good rebuilt if possible. Any ideas?

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)