I was driving a defender up Licola way and dissengaged the rear arb locker to late, thought I'd broken something.
A torsen type diff will only ever want to equalise the torque between the two wheels, not the rotational speed. They do however need torque applied to both axle sides, and the more torque differentiation that occurs the more they lock which is why they amplify the effectiveness of traction control. However, if a wheel is in the air no torque can be transfered on that side, but again, the traction control transfers that torque.
There's a few good articles on wikipedia.
