[rotorwrench]

The ground path breaker in the operating solenoid may have a problem or a wire in the kill circuit may be shorting to ground. When the kick down switch is activated, all it does is open the circuit on the holding coil then closes the ignition coil kill circuit so the transmission will drop out of overdrive. The moment that it drops all the way out, a set of points inside the solenoid opens and allows the ignition coil back on line. It's not hard to take the outer can lid off and check out the functions inside the solenoid. There are two sets of points so you have to figure out which one grounds the coil and which one opens the circuit on the pull in coil. The terminal connections inside will generally lead you to which terminal's points to look at. The solenoid has a pull in coil and a holding coil. As soon as the unit pulls the transmission all the way into overdrive it kicks out the pull in coil function but leaves the holding coil on line. This feature saves a lot of electrical power usage that would be unnecessary to the operation of the system.