Shifting between 3rd Gear and 4th Gear
As the speed of the vehicle reaches the programmed value, the PCM turns shift solenoid valve C OFF, and uncovers the shift solenoid valve C pressure port (SC) to shift valve C. Shift solenoid valve A remains ON, and shift solenoid valve B remains OFF. Shift valve C is moved to the right side to switch the line pressure port (4) and CPC B pressure port (4B) leading to the 3rd clutch. Shift valve C also uncovers the CPC A pressure port (4A) leading to the 4th clutch. The PCM actuates A/T clutch pressure control solenoid valves A and B. A/T clutch pressure control solenoid valve A pressure (56) is applied to CPC valve A, and A/T clutch pressure control solenoid valve B pressure (57) is applied to CPC valve B. CPC valve A regulates line pressure (4), and line pressure (4) becomes CPC A pressure (4A). CPC A pressure (4A) flows to shift valve B via shift valves C and A, and becomes 4th clutch pressure (40) at shift valve B. 3rd clutch pressure (30) is changed to CPC pressure, and the 4th clutch is engaged by CPC pressure. The 1st clutch is also engaged, but no power is transmitted because of the one-way clutch.