The throttle pedal is in the halfopen position, developing throttle pressure, which is directed to the kickdown valve. Throttle pressure is also directed to the throttle plug of the pressure regulator valve. Throttle pressure moving the throttle plug forces it against the throttle plug spring tension. The action of the throttle plug removes some of the opposition to the pressure regulator valve spring, resulting in a boost in line pressure. Throttle pressure moves to the 1-2 shift valve, where it is blocked by the upshifted valve’s spool land. After seating check ball 5, throttle pressure and coil spring tension push on the 2-3 shift valve reaction area and move it to the downshifted position against governor pressure. Throttle pressure leaves the 2-3 shift valve to hold the shuttle valve throttle plug against its seat.