Re: Overdrive not working

Posted by HH56 On 2016/7/24 20:46:25

The relay should come in when governor reaches speed -- roughly 17-20 mph and will stay in as long as you are above the governed speed or have not done a kickdown. The solenoid will also stay energized since thru the relay is the only way it gets power. It will stay that way and not go into OD until you momentarily let off the accelerator.

Letting off the accelerator slows the engine but the tires are still turning at speed. That slight momentary speed difference lets parts in the OD shift around and line up parts to unblock the path so the solenoid can fully push the pawl into the sun gear. Once the sun gear is locked you are in OD.

When you press the accelerator all the way to the floor and hit the kick down switch the relay and solenoid will drop out and stay out as long as the accelerator is held all the way down as it might be when passing a car. As soon as you let the accelerator relax a bit from full throttle -- even a tiny amount -- so the kickdown switch closes again, with the car still going above the governor speed the relay will re energize and power the solenoid again to get ready to go into OD.

It will stay that way again and not go back into OD until you momentarily let off the accelerator and repeat the mechanical process.

One possibility on the relay clicking is the rivets connecting the terminals have become oxidized or loose and are making poor contact. That can happen if the terminals are subject to force or if the phenolic material they are mounted to shrinks a bit.

Repro and used relays are available if you need a new one but others have elected to save the $200 or so by taking the old components out of the can and install a modern 40 amp cube type relay in its place. The modern relay fits in the can nicely, is totally hidden and costs around $10.