you must have experienced such a situation or noticed that when #friction between a #wheel and ground decreases, the wheel spins quickly or slides while the other wheel stops .To solve this problem, torque-sensitive gears are invented (Torsen) where the movement is moved from the pinion gear to the crown gear as in the differential gears,
where the case mounted on the crown gear moves and contains a set of worm gears .
As we talked before that the movement is possible to move only from the worm gear to the worm wheel and not vice versa ,
so when the car is in a straight line, the movement moves from the case to the worm wheel, which is locked with the worm gear, the whole set is locked and moving as one piece
When driving a bend, the outer wheel will take a longer path,
so the worm gear will move the worm wheel connected to a spur gear , transporting motion to the worm wheel of the other wheel in opposite direction , causing a decrease in internal wheel rotation as much as the increase rotation of the external wheel
In the event that one of the wheels fell in the clay hole or rose from the ground,
it will not be able to rotate alone because the movement is transported only from the worm gear to the worm wheel and the movement of the transmission must cross first the worm wheel, then the set will lock and move as a single piece as we said earlier .
In this video there is an animation of Torsen gears that we have explained
The disadvantages of this system are the high cost of manufacturing and the difficulty of assembling it in addition to high noise .See Similar Products
Source : learnengineering.org