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Hydraulic control system

Hydraulic control system




The hydraulic control system consists of an oil pump with pressure control valves, valve housing with shifting valves and accumulators, clutches and brakes.

Depending on the pressure built up by the pump and the selector lever position, the hydraulic control system controls the hydraulic pressure that actuates the torque converter clutch and other clutches and brakes to suit the current type of driving.

There are 4 solenoid valves in the valve housing. Solenoids S1 and S2 are activated when supplied with current from TCM and control the shifting valves so that gear shifting takes place. TCM uses information on the input/output speeds of the transmission and the position of the accelerator pedal to shift gear at the correct moment.

When supplied with current by the TCM, solenoid SL is activated and engages the Lock-up function in the torque converter so that direct drive is obtained. The TCM activates the Lock-up function in 3rd or 4th gear, de pending on the position of the accelerator and the speed of the car.

Solenoid ST is supplied with PWM-controlled current. System pressure is regulated so that it is proportional to engine torque, resulting in improved shifting performance and reduced mechanical wear on the transmission. The TCM uses information on the current engine torque and selected gear to control system pressure.