TRANSMISSION 1804714 - Caterpillar

Illustration 1 g00535272
Selector and pressure control valve in NEUTRAL with a stopped engine (1) Passage (2) Passage (3) Priority reduction valve (4) Neutralizer valve (5) Rotary selector spool (6) Chamber (7) Chamber (8) Passage (9) Relief valve for transmission charging (10) Transmission lubrication relief valve (11) Chamber (12) Passage (13) Spring assemblies (two) (14) Cam (15) PassageThe selector and pressure control valve controls the flow of oil that goes to the pressure control valve. The selector and pressure control valve consists of five valves. The following chart provides the basic function of each valve.
Table 1
Operation Of The Components In The Selector And Pressure Control Valve    
Valve     Function    
Priority reduction valve (3)     This valve controls the pressure of the pilot oil that is available to rotary selector spool (5).    
Neutralizer valve (4)     When the transmission is not in NEUTRAL and the engine is started, this valve stops the flow of pilot oil to rotary selector spool (5).    
Rotary selector spool (5)     This valve sends pilot oil to the pressure control valve. This pilot oil determines the transmission clutches that will be engaged.    
Relief valve (9)     This valve controls the maximum charging pressure in the transmission hydraulic system.    
Transmission lubrication relief valve (10)     This valve controls the maximum pressure of the lubrication oil that is going to the transmission.    Priority Reduction Valve
At the selector and pressure control valve, the oil from the transmission charging pump section flows to several locations. The oil flows through passage (1). Some of the oil flows through passage (2) to the upshift solenoid and to the downshift solenoid. The remainder of the pump oil flows to priority reduction valve (3). 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 (3) .As the oil pressure increases, the oil moves the priority reduction valve downward against the force of the spring. The pressure of the oil that is flowing from priority reduction valve (3) to neutralizer valve (4) is controlled by the priority reduction valve.As priority reduction valve (3) moves downward, pump oil in passage (1) flows through passage (8). Some of this oil flows to relief valve (9). Relief valve (9) controls the maximum charging pressure in passages (1), (2), (8), and (15). Some of the oil from passage (8) flows through passage (15) to the pressure control valve.