Abstract: This invention relates to a double reduction tandem axle driving unit comprising a housing with a plurality of walls and a flange to secure the housing to a drive axle's housing. The drive shaft is journalled in said housing and a bevel pinion is disposed on said drive shaft. A cross-shaft is journalled in the front and back walls of said housing at generally right angles to said drive shaft. A bevel gear is on said cross-shaft, and meshes with said bevel pinion of said drive shaft. A spur pinion is on said cross-shaft near said bevel gear and a spur gear is secured to a carrier of a differential mechanism for said drive axle. The spur gear meshes with said spur pinion and said flange is provided with an aperture for passing said bevel gear and said spur gear. A first bearing is disposed at the end of said cross-shaft where said bevel gear is located and a second bearing is disposed at the opposite end of said cross-shaft where said spur pinion is located.