I've got a '78 262 with an M46 transmission. Drive train has 105,000 miles on it. Occasionally when attempting to disengage the overdrive the od stays engaged until I shift into third. After a few seconds of being in third gear I can feel the od disengage and rpm increase. This happens mostly on longer drives. The dash od light follows the switch action fine. Also I don't have a problem getting the od to engage. I'm contemplating having the od unit rebuilt at a shop but would like to see if any odites might offer an opinion on what is the issue. Tranny fluid was replaced at 100,000 with type F non-synthetic. Thanks