Took a trip this weekend. On the way back. I tried to set cruise at 65 and it would stay in 5th gear until I was either going downhill or reduced the cruise so it would change to 6th. It did this at all speeds up to 76. At 77 it would drop to 6th and pretty much stay there except on uphill climb. This just started doing this and I have not had any problems before. I have about 3600 miles. Any others with similiar problems?