This B&M-supplied diagram shows the correct placement of the cooler in the transmission cooling circuit. Notice the direction of flow shows that the cooler is located downstream of the heat exchanger in the radiator and directly before the fluid return to the transmission. The B&M instructions explain how to determine which line is the fluid return line according to your make of vehicle. We were certain to be correct in this determination because the B&M external cooler works to improve on the cooling job done by the factory heat exchanger. To do this the cooler needs to be last in line before the fluid returns to the transmission.