An axle driving apparatus which has a housing and a hydrostatic transmission therein separate from the housing with fluid conduits in a center section connected to hydrostatic rotatable cylinder blocks operatively connected to axle shafts, the improvement involving check valves associated with the fluid conducting conduits and including check valve balls to affect fluid flow through the conduits and being positioned to move in a vertical path in a direction at right angles to the axes of the axle shafts, and a movable bypass arm mounted in the housing and movable to open or close the fluid conduits.