Driving in 1st Gear
The PCM turns shift solenoid valves A and BON in 1st gear. Shift solenoid valve B is turned ON from OFF to apply the shift solenoid valve B pressure (SB) to shift valve B. Shift valve B is moved to the right side by the shift solenoid valve B pressure (SB) to close the line pressure port (4B) leading to shift valve C. As the line pressure (4B) from shift valve B is not applied to shift valve C, shift valve C is moved to the right side by a spring force to connect the line pressure port (4) on shift valve C and the 1st clutch pressure port (10). With this shift valve C movement, the line pressure (4) from the manual valve becomes 1st clutch pressure (10) at shift valve C, and flows to the 1st clutch. Then the 1st clutch is engaged by 1st clutch pressure (10).