While cruising at highway speeds the Transmission will periodically shift down, then back up, as if on a steep hill. Does it wether the O/D is on, or off, same in cruise control. If I pull over and restart the engine, it solves this about 1/2 the time, but fuel economy has suffered since I developed this issue. I continually monitor the fluid condition and level which is fine. Is this an electrical malfunction? I have been scouring the archives here, and other sites but can't seem to discover much about this. Thank you for the read. Your time and knowledge appreciated.