1997 Oldsmobile 88 Slips out of " Overdrive"

I'm having transmission problems on a 1997 Oldsmobile Delta 88 with 175000 miles, after 4+ hours of driving via Interstate. Every so often my transmission will slip out of gear (OD) and redlines, this will occur 2-3 within a 1000 miles. Each time I must downshift and sometimes I can only travel at speeds between 50-60 mph. After 10 mins. Of babysitting, all is back to normal and it might not happen again for another 300-600 miles. Someone suggested this could be the engine and transmission failing to communicate via an electronic sensor? I've googled several different words and have had no luck, any suggestions?