The differential is located within a housing (10) which turns about an axis L. Two sun wheels (30L,R) move co-axially and turn within the housing. Each wheel has an outer section with inclined teeth (32) and an inner wedge section (31) linking the end of a drive shaft to the inner face. Each has planetary wheels (40) which turn within the housing. Each pair of planetary wheels is in contact with the pair of sun wheels and each other. Both ends of the sun wheels in the differential mechanism are joined to a flange (35) which has a larger diameter than the toothed section of the sun wheel. The presence of this flange increases the frictional contact surface area (33) within the effective frictional radius.
