Automatic Transmission Secondary Fluid Pump Assembly
The purpose of the Automatic Transmission Secondary Fluid Pump Assembly (1) is to fill the forward clutch with fluid in order to keep it lightly applied. Maintaining the forward clutch hydraulic capacity will ensure rapid clutch engagement during the engine restart cycles, eliminating engine flare or sudden transmission engagement.
The secondary fluid pump assembly is a gerotor type pump with an airtight electrical motor. The motor has a built-in electromagnet compatibility (EMC) and is a permanent magnet stator with a wound rotor. The pump is a external/internal toothed constant displacement pump and has a built-in pressure relief valve (2). The pump assembly utilizes a replaceable 60-Micron filter (3) and does not require regular maintenance. The pump assembly mounts to the valve body and is submerged in the transmission fluid sump.
As the motor drives the pump gear, a low-pressure area is created between the gear teeth. The fluid volume is positively displaced, thereby creating suction at the pump inlet. As the fluid space between the rotating gears lessen, high-pressure fluid is created and supplied to the manual valve where it is directed into the forward clutch hydraulic circuit. A check valve installed in the valve body located at the pump outlet prevents fluid from the main transmission oil pump from flowing into the secondary fluid pump.