Climbed in my 98 F150 FWD to go home last night and started getting a flashing "overdrive off" light. I pulled over, stopped the engine, restarted and it cleared. Same thing happened this morning.
Any clues? Sensor? Transmission about to shell out? I just serviced the transmission for the second time at last oil change (67,000) and it seems to run just fine.

 

Update: The Ford shop called to say my torque converter is trash. The flashing light resulted from the sensor filling up with shrapnel from the disintegrating torque converter. No insight into why it failed. My service writer said, and I quote, "Hell, there's no telling when those torque converters will go". Now there's a comment to give you a warm fuzzy feeling.
Thanks to the extended warranty, a $2200 transmission will cost me $50, but my faith in the vehicle is somewhat diminished.