One thing you might consider...when the car is first starting up the 4Matic is always automatically engaged. this means that if you are just starting up and turning a tight corner, as you probably will be doing in a "U" turn, the 4Matic has all wheels engaged. Once you are over the 12mph or so speed, and there is no road condition requiring it, the 4Matic system shuts down. As you state, when the system is in "test mode", which is essentially turned off, you do not feel this condition.

SRHarvey,