Found a reference to them
According to a post on a Benz forum, apparently they are open.
I think the below is the modern ML320
EDL (often referred to as Electronic Traction Control.)
This system is used by most VW models today, many Audis and several other car models, and was first introduced for offroad use in the Mercedes ML320 (AWD) and is undoubtably used by many others today.
It's what I call the poor man's LSD. (Some people dislike my characterization of it, as it can be very finely tuned, but it's still very cheap to implement and has some reliability and torque handling problems.)
This is an electronically regulated speed sensitive system using the two independent ABS channels. Start with an open differential and go back to Example 3. You're holding onto the right output shaft while the input shaft turns. Now add a disc brake and rotor on the left input shaft.
Activate EDL system. When the computer senses a speed imbalance between left and right, (remember the left shaft is spinning at 2X and the right is not moving at all), it simply applies the brakes to the left side output shaft. The open differential immediately tries to balance the torque. You will feel it trying to turn the right side immediately. If it can grab the left harder than you're holding the right (which it most certainly can and will) then it would immediately transfer some rotation to the right output shaft and it will twist out of your hand. If you could hold onto the right side hard enough (weld it the side of a tractor trailer truck) , it would be forced to slip the left brake disc, or stall the engine.
Link is
http://www.houseofthud.com/differentials.htmhope it helps
Kubes
Transfer
