PISTON-CYL 2389347 - Caterpillar

Priority Reduction Valve
At selector and pressure control valve (6), the oil in passage (1) from the transmission charge pump section flows to two locations. Some of the oil flows through passage (2) to the upshift solenoid, to the downshift solenoid, and to the lockup clutch solenoid. The remainder of the pump oil flows to priority reduction valve (14). The oil flows through an orifice in the priority reduction valve. This oil opens a check valve. The oil then flows to the upper end of priority reduction valve (14). As the oil pressure increases, the oil moves the priority reduction valve downward against the force of two springs (16). The spool for the priority reduction valve will shift to metering point (11) in torque converter drive and to metering point (23) in direct drive.Torque Converter Drive
Priority reduction valve (14) shifts to metering point (11). In torque converter drive, the oil that is flowing from priority reducing valve (14) to neutralizer valve (7) is controlled by the priority reduction valve. When neutralizer valve (7) is moved downward, the oil flows into chamber (10) of rotary selector spool (5). Chamber (10) has a screen that filters the oil. This oil is able to flow to the pressure control valve. This pressure oil is the pilot oil that controls the movement of the selector pistons in the pressure control valve.The oil in passage (1) from the transmission charge pump section flows around the spool for priority reduction valve (14) to dual stage relief valve (17). In torque converter drive, dual stage relief valve (17) controls the maximum pressure in passages (1), (2), (13), and (21). Some of the oil from passage (13) flows through passage (21) to