Originally Posted by Jim Hef
Brake application stops the airborne wheel from spinning throwing the power to the other wheel. 4wd is a misnomer...only two wheels are driven in any system.
Thats not really technically correct.
The computer can partially
brake the spinning wheel, sending a percentage of torque to the laden wheel while retaining some available torque in preperation for the unladen wheel becoming laden again.
It doesn't behave like a switch.
Still not ideal in soft terrain situations.