Abstract: Each of two drive wheels on a vehicle is independently driven by a wheel motor having four single acting hydraulic cylinders. Both wheel motors are supplied by a common engine driven pump. Two forward speeds are provided by a valve arrangement which can circulate the hydraulic fluid through all four, or only two, cylinders of each motor. Valves in a pair of valve units are shifted rapidly by camshafts and snap acting mechanisms to control the motor cylinders. Reverse drive is accomplished by a timing adjustment of the camshafts. The conventional gear differential, speed change gears and reversing gears are thereby eliminated.