How It works:
In the Torsen, as in any other differential, the power of the engine is transferred to the differential housing via the ring gear. The Torsen then uses pairs of worm wheels (from two to three pairs, depending an the size of the differential) mounted on the differential housing to turn the worm gears splined to the axle shafts. The left worm wheel of each pair turns the left axle shaft, and the right worm wheel of each pair turns the right axle shaft, Because the worm wheel cannot turn the worm gear, it locks on the gear and turns the axle shaft, propelling the vehicle forward. The right and left axle shafts (and right and left wheels) turn simultaneously. Each wheel then rotates at the same speed.
However, when the vehicle makes a turn, each wheel rotates at a slightly different rpm. For instance, during a left turn, the left wheel will slow down by two rpm, and the right wheel will speed up by two rpm. One axle shaft always slows down at the exact rate that the other one speeds up. This difference in rpm is transferred to the worm wheels (because the worm gear on the axle shaft can turn the worm wheel and equalize the other side via the 1:1 spur gears, which act as balancing gears). So the engine is "Locked" or engaged on the axle shafts, while allowing for differential action when negotiating turns.