Torsen Center Differential

As already mentioned, the center (or interaxle) differential is needed to balance the forces between the front and rear axles. (The front and rear axle differentials operate independently of it.)

It is located at the rear, in one unit with the transmission.

By the way, the name Torsen comes from the Gleason company, a manufacturer of gearboxes, where this differential was invented. The name is an abbreviation of the English words Torque Sensing, meaning roughly "torque-sensitive". Thus it is in a way a description of its action:

This differential transmits a greater drive force to the axle with better road grip.

This occurs in such a way that one axle can transmit 3.5 times the force of the other.

But with equally good surface conditions (under both axles), the traction force is distributed evenly between the front and rear axles – no preference for either driven axle.

Principle of Operation
The Torsen differential is based on the worm gear principle and uses its basic principles:

A worm gear can be designed to have a high or low locking ratio.

The value of the locking ratio depends on the lead angle of the worm, that is, on how many flat or steep threads the worm has.

An example of a flat worm with a high locking ratio is a car jack. The drive handle, acting on the worm, raises the vehicle, but the vehicle, despite its weight, can never turn the drive handle and lower the jack.

Design
Thanks to an ingenious design consisting of eight worm wheels and 12 pinion gears, combined with the differential housing, hollow shaft, and front and rear drive axles, the action described in the previous section is achieved in the best way.