Abstract: A differential unit has axially aligned helically toothed output gears of different diameters to provide an unequal division of the input torque, in meshing relationship with two sets of intermediate gears which mesh together and are rotatable on axes parallel to the output gear axis. The gears of one set of intermediate gears mesh with concentric internally and externally toothed output gears to provide alternative outputs at different torque division rates. Slip within the unit can be opposed by frictional coating on the gears and/or on the housing by which they are carried and/or by a damping fluid which may be an electro-rheological fluid.