YOu can test the solenoid by listening for it to click when flooring throttle (ign on, not running). If it doesnt click, check switch (under pedal?) - short the pins, check fuses etc. if all is good here, find electrical lead on box, check that its getting 12V when pedal floored. If it is, apply 12V directly to solenoid, with ground on box body, check for click. If this all works, your TV cable probably needs adjustment to bring it into the area where kickdown will work. take care, the adjustment can be sensitive. These are my experiences with old 3 speed anyway - 722.0?
jp