Controlled differential device

A controlled differential device comprises a pair of epicyclical gear trains each comprising a sun gear (44,45), planet carrier (54,55) and annulus (48,49). The sun gears are rotated in mutually opposite senses by a motor (41), the planet carriers are interconnected by a shaft (43) such that they rotate in common, and output shafts (50,51) are coupled to the annuli. Also disclosed are drive configurations for a skid steered vehicle incorporating the controlled differential device.