Abstract: An improved closed-loop hydrostatic transmission system is provided of the type including a pump (11), a motor (13), and a pair of conduits (15 and 17). The system includes a main control valve (43) and a charge pump (23) which is the sole source of make-up fluid to the closed-loop system and the sole source of control fluid for varying the pump. The system includes a power limiting means comprising first and second pressure relief valve means (75 and 77) operable to provide fluid communication from whichever side of the closed-loop is at high pressure to the system reservoir whenever system pressure exceeds the predetermined maximum pressure. The motor is adapted to transmit drive torque to a reversible load (37) of the type having a known inertia and a predeterminable time of deceleration from maximum speed operation in one direction to a standstill condition.