The oil cooler for the engine transmissions is mounted on top of the combining transmission. It receives cooling air from the fan assembly mounted on top of the combining transmission. Oil Circulation Oil is circulated in each transmission lubrication system by two separate elements of the six-element lubrication pump in the combining transmission. Oil flows from the oil tank through the pressure pump, through the filter and relief valve assembly, through the oil cooler, and through the check valve. Then the oil flows into the transmission where it is sprayed on the gears and bearings by various jets.
Oil is scavenged from the sump by the scavenge section of the oil pump and returned to the oil tank.
The combining transmission is a central collection and distribution point for the drive system. The combining transmission is mounted in the lower forward section of the pylon. Torque from the engine transmission is transmitted by the combining transmission and the forward and aft synchronizing drive shafts to the forward and aft rotary-wing drive transmission. Speed reduction is also attained within the combining transmission. The output shaft drives the lubricated pump.