i have a 1978 245 4-speed manual with electric overdrive. sometimes when im driving with the overdrive engaged, it will downshift into 4th for a quick second, and then pop back into 5th (OD). does anyone have any ideas how to go about fixing this or testing it?

chris, check out my recent post in regard to the overdrive.

"Overdrive kicks in and out" posted on Dec 29


Robert

I forget to mention. If the OD light on the dash goes off when the OD quits, the problem is definitely electrical.

If the overdrive is clicking on and off, the problem is most likely electrical. When my old GT had the same symptoms, it ended up being worn insulation on the wires that run through the shifter. As I recall, the two wires have a connector under teh carpet just to the right of the shifter. You should be able to disconnect the wires at the shifter switch and pull them through the shift column one at a time w/o too much difficulty. Somebody told me they replaced the wires w/ heftier wiring, but I had already just wrapped the bare spots w/ electrical tape, so I didn't redo the job. Hardest part was threading the wires back through the column. If the wiring there is OK, check the wiring all the way to where it goes under the car, and if you still can't locate a problem area, it's time to get under the car and take a look.

Good Luck