RING-RETAINING 8T3293 - Caterpillar

Illustration 1 g00338136
Priority Valve Group (1) Opening from the transmission oil pump (2) Opening to the lockup clutch valve spool (3) Opening to torque converter (4) Priority valve (5) Opening to the selector valveThe priority valve ensures that pressure oil is available for the synchronizing valve and the shift cylinder before the oil goes to the clutches.The priority valve (4) controls the pressure of the oil to the selector valve. The priority valve works with the lockup clutch and synchronizing valve in order to keep the tractor transmission and the scraper transmission in the correct relation. If the tractor and scraper transmissions are not in the correct relation, the synchronizing solenoid closes. When the synchronizing solenoid closes, pump oil will be allowed to flow to the torque converter. The pump pressure at the priority valve is now less than the setting of the priority valve. The priority valve will close. The oil to the selector valve and the clutches is stopped. When the tractor transmission and the scraper transmission are in the correct relation, the synchronizing solenoid will open. When the synchronizing solenoid opens, the pump oil will be held in the lockup clutch and synchronizing valve. The pump pressure at the priority valve is now greater than the setting of the priority valve. The priority valve spool will move to the left. This allows the oil to flow to the selector valve.For more information about the priority valve, refer to "Systems Operation"section of Systems Operation, Testing and Adjusting, "Transmision Hydraulic Control Operation".