In a closed loop hydrostatic transmission circuit, a low side hot oil shuttle valve is used to discharge supercharge oil from the low side of the loop for cooling. This shuttle valve is piloted from the pump work ports, with the highest pressure shifting the valve so that the opposite (low pressure) side of the loop is connected to tank (typically through a hot oil relief valve, into the motor case).

Models FMDB and FMDA are Sun's new 2 position, 3-way electro-proportional meter-in throttling valves. These versatile cartridges can be configured into a variety of motion control circuits.