My 98 Countour 4 cylynder automatic drives great, even with check engine light on for a year! But after a 10 to 15 minute sustained high speed (interstate) drive, once you come to a stop it will hard shift from first into second. We have learned that if we simply turn off the car and restart it the hard shift goes away and the car is fine until the sustained high speed drive takes place again. Any quick ideas what it could be? Speed sensor was replaced on transaxle. No change.