SUPPORT AS 3W2843 - Caterpillar

Illustration 1 g00288426
Location of the priority valve (1) Priority valve
Illustration 2 g00288427
Components of the priority valve (2) Solenoid (3) Passage to the torque converter (4) Adjustment screw (5) Locknut (6) Drain to bevel gear case (7) Spool assembly (8) Passage from the torque converter and lubrication section in the oil pump (9) Check valve assembly (10) Slug (11) Slug chamber (12) Passage to steering, brake and transmission controls (A) Flow from the torque converter and lubrication section in the oil pump (B) Flow to the torque converter (C) Flow to the power train oil filterThe priority valve is located at the front of the bevel gear case. The power train oil filter is mounted on the priority valve.The priority valve makes sure that oil pressure is first available for steering, braking, and transmission control, and then for torque converter operation and lubrication of the steering clutches, brakes, and transmission.The priority valve has two modes of operation. In the normal mode, oil flow to the torque converter, the lubrication system, and the controls are separate. No priority is given to the flow to the controls.In the priority mode, oil flow to the torque converter and the lubrication system have priority in order to maintain pressure for steering, braking, and transmission control.The priority valve setting for the flow mode is determined when on/off solenoid (2) selects oil from either inlet (8) or drain (6) in order to supply chamber (11) .For the normal mode, the solenoid is ON and inlet (8) is selected.For priority mode, solenoid (11) is OFF and drain (6) is selected.The electronic control module controls the current to the solenoid.No current is sent to the priority valve under specific operating conditions in order to maintain adequate pressure to the steering and brake controls and the transmission controls. If no current is applied the priority valve operates in the priority mode. The priority valve is at high pressure in this mode. No current is applied to the priority valve during the following conditions:
Engine speed that is less than 1300 RPM
Power train oil temperature less than 40°C (104°F)
Changes in transmission speed
Directional changesIn the normal mode, inlet pressure in chamber (11) acts on more of the spool area around slug (10) . This causes spool assembly (7) to move toward adjusting screw (4) . This allows oil from the torque converter and lubrication section of the pump to pass through the priority valve to torque converter (B) .Oil from torque converter and lubrication section (A) of the oil pump enters inlet passage (8) in the priority valve. The oil goes from inlet passage (8) through a hole in spool assembly (7) . The oil then goes into chamber (10) between the slug and the poppet.When the oil pressure in chamber (10) becomes higher than the priority valve setting in the current mode of operation, spool assembly (7) moves. The spool assembly moves toward adjusting screw (4) and