I've never seen a Mercedes LSD unit, but it's probably clutch discs and a spring setup just like a fords 8.8

Whenever I regeared my mustang, I used two sets of clutch discs and packed the sucker as tight as it would fit. It was a pain to assemble, but had enough bite to chirp the tires in low speed turns for the first couple thousand miles.

I would try doing this if possible to your Benz unit.