Originally Posted by panzerfaust
From what I've read on the forums, xDrive maintains a normal 40/60 split between F/R in normal conditions, and adjusts those values when slippage occurs. Over a certain speed (highway travel), I've heard the vehicle becomes full RWD.
+1 there is another thread regarding this so
...but I believe it was over something like 60 or 65mph it becomes full RWD