OUTER RACE 5P3968 - Caterpillar

The main components of the charge pump include:
Housing
Pump body
Ring gear
Pinion Gear
Illustration 1 g06087965
Left view of transmission
(1) Charge pump (transmission)
Illustration 2 g06088024
Simple gerotor and crescent pump diagram
(2) Pump body outer shell
(2A) Crescent (part of pump body outer shell)
(3) Ring gear
(4) Pinion gearThe charge pump (transmission) (1) is on top of the transmission.The pump housing encloses the rotating components of the pump drive. Charge pump lubricating oil uses the pump housing as a return path to the transmission sump.The pump body consists of the outer shell (2) and the valve plate. The outer shell is o-ring sealed to the valve plate.Ring gear (3) is driven by pinion gear (4). The pinion gear is driven by the transmission charge pump drive gear which is driven by the torque converter impeller housing.The pump body and gears are a matched set and are serviceable as a single unit.As the ring and pinion gears rotate, oil is drawn into the suction side of the pump. The suction side of the pump is the side of the ring and pinion gear set before the crescent (2A). Suction is created by the widening of the area between driven gear teeth. Oil is then forced to travel around the crescent, and into the discharge side of the pump. Discharge pressure is created by the narrowing of the area between the gear teeth, as the gears rotate. The oil in the discharge side of the pump cannot be compressed and therefore travels out of the pump, under pressure. Discharge pressure is controlled by the charge pump relief valve.