Abstract: A first wheel positioned on a first side of a vehicle is driven by a first reversible hydraulic motor. A second wheel positioned on a second side of the vehicle is driven by a second reversible hydraulic motor. A first valve controls the drive direction and speed of operation of the first hydraulic motor. A second valve controls the drive direction and speed of operation of the second hydraulic motor. An actuator shaft is connected with the first and second valves. Linear movement of the actuator shaft along its axis actuates both of the valves in either a forward or a reverse direction. The actuator shaft is also rotatable about its axis. Rotation of the actuator shaft about its axis actuates one of the valves in the forward direction and the other of the valves in the reverse direction.