A vehicle differential unit in which an input or drive pinion is mounted on a shaft which is supported on two axially spaced bearing assemblies carried by a housing which encloses the unit. The housing is provided with first and second apertures, the second aperture, which is provided with a detachable cover, being of sufficient size to pass the drive pinion and the first aperture not allowing the passage therethrough of the drive pinion. A first bearing assembly, which is supported in the first aperture, supports a first end portion of the shaft with which a vehicle drive shaft is normally associated and a second bearing assembly, located on the other side of the drive pinion from the first bearing assembly, supports a second end portion of the shaft which is located within the housing adjacent a crown wheel of the differential unit. The second bearing assembly is mounted on a bearing support which is separate from the housing and is secured to an abutment surface on the housing by releasable means so that the bearing support can be inserted into the housing through the second aperture and, after the first end portion of the pinion shaft has been received in the first bearing assembly, the second bearing assembly can be located on the second end portion of the shaft and the releasable means then engaged to secure the bearing support to the housing.