Abstract: A locking differential comprising a differential carrier1 housing a pair of bevel gears 2, 3 and at least one pinion gear 4 which meshes with the pair of bevel gears, a locking ring 6 positioned within the differential carrier1 between the carrier and one of the bevel gears and splined to the carrier 1 at 7 and 8, locking teeth 9 on the locking ring 6 and corresponding locking teeth 10 on the bevel gear 3, an annular cylinder 12 formed in the carrier 1 and receiving a piston 11 and seal 11 a, the piston 11 being integral with the locking ring whereby the charging of the cylinder 12 with compressed air causes the locking ring 6 to move into its locking position with the teeth 9 engaging the teeth 10 against the action of springs 13 to lock the differential. The locking ring is located within a shaped cover plate C which closes the differential carrier 1 and provides bearing support for the bevel gear 3.