[Kevin M]

Let's set aside this argument over the nuts and bolts of DCCD operation and discuss why it does what it does. In non-DCCD, OE Subaru AWD systems, you have 50/50 torque split all the time. The biggest disadvantage of that is the added workload of the front tires when turning and accelerating reduces available grip. By moving more of thetorque rearwards, there is more grip available up front. The reason for the locking characteristics of the DCCD are what sperry just posted- it's to use wheelspin in the rear to force the front tires to carry more acceleration load as the lateral load is reduced as you unwind the wheel coming out of the turn.