Have had a problem with my transmission shifting into overdrive. Drove it yesterday and it shifted into overdrive perfectly for about 12 miles of stop and go on country roads. As I approached my destination I hit the left turn signal and it downshifted to 3rd at about 50 mph. After that and on the way back home it stayed in 3rd. I think I have a electrical gremlin in my steering column somewhere. Any ideas appreciated.