Abstract: A tractor transmission wherein an engine output is transmitted through a clutch mechanism to a primary change speed mechanism, and a clutch housing and a first transmission case are removably connected to each other. The first transmission case includes a space in a forward portion thereof to accommodate a high speed and low speed switching mechanism and a forward and backward switching mechanism, interchangeable with each other, to be attached to a rear wall of the clutch housing.

Abstract: Disk brake apparatus mounted on a differential gear shaft extending from each side wall of a transmission case. A cam plate and balls coact to press a brake disk mounted on the differential gear shaft against a friction surface. Each of the balls is in direct or indirect point-to-point contact with the outer side wall of the transmission case to reduce the sliding resistance involved.

Abstract: Construction for uniting by welding a brake case cover, a rear wheel axle case and a terminal speed reduction unit case which are all made of sheet metal. The rear wheel axle case has at its opposite ends precisely circular tubular portions fitting in the brake case cover and in the terminal speed reduction unit case to connect them together. The united parts are joined together by automatic welding. The rear wheel axle case has a flat tubular intermediate portion for mounting a fender or the like thereon. The flat tubular portion has a smaller sectional area than the opposite end tubular portions so as to be substantially flexible and to thereby absorb concentric loads on the weld joints.