I was at borders books store the other day and found a really cool book on the older E class up to 1995. A lot of it is for buying a used Mercedes but it has a lot of secrets to reveal, like special tools for doing an alignment, bleeding brakes, checking clutch thickness without opening up the bellhousing, etc...
Anyways I stumbled across a page describing an optional electric locking diff for the diesel models, as we all know we have peg leggers, and installing a posi unit gives 35% lock up to the other wheel or there abouts. while the diesel electric unit can give a full 100% lock up at anytime. I completely forgot to write down the part number but will go back an purchase the book later. I'll have to ask around the MBZ forums and see what the deal is and what are the dimentions. If the parts are still available from a wrecking yard or the dealership this might be a viable option for a rear end upgrade, that is if, the dimentions are close enough to bolt in there. Might be worth considering for an autoXr, even at $1,500, unless 100% lock up is too much?

Let you know what I find out...