GENERATOR AR 4W8958 - Caterpillar

Illustration 1 g03487876The transmission hydraulic control relief valve is used in order to regulate the pressure to the main components in the transmission. The transmission hydraulic control relief valve also provides oil to the torque converter.Oil enters the relief valve at oil supply port (1). The pressure of the oil acts on spool (6). Spool (6) moves to the right when the pressure that is acting on the spool is greater than the force of spring (8). Oil flows to the chamber for the torque converter inlet (5). When spool (6) moves to the right, oil enters chamber (3) past check ball (4). Under normal operation, oil in port (1) seeps past spool (6) at point (10) to the torque converter. As the pressure of the oil to the torque converter rises, relief valve (9) allows the oil to escape to the sump. Relief valve (9) controls the inlet pressure of the oil in the torque converter.If the oil supply to the transmission hydraulic control relief valve is stopped, the oil in chamber (3) is trapped by check ball (4). This oil can escape slowly past slug (2) to the sump allowing the spool to return to the left. Slowly escaping oil past slug (2) prevents spool (6) from returning to the left before the torque converter has stopped rotating.Adjustment screw (7) alters the preload on spring (8) in order to adjust the relief pressure.