Abstract: A compact, light weight and easily maintainable differential gear unit casing is provided which comprises a box-like housing having front, rear, top, bottom and two side panels. Each of the front and rear panels has an aperture; which is at least partially axially aligned with each other; and bearing means cooperating with the aperture and demountably secured to the front and rear panels, the bearing means being coaxially aligned with the aligned portions of the apertures on the front and rear panels. Each of the side panels has an opening which is at least partially aligned axially with the other; and axle supporting bearing aligned coaxially with aligned portion of the opening on the side panels and is adapted to have the driving axles journaled in the bearing.