I have a 1992 Cavalier with 105,000ish miles on it. One day I mistakenly let my mother drive it to work because her car was in the shop and I had an S10 that I could use. Well come 5:30 pm I get a call that she is up at the gas station and she cant get it to start. So I go there to learn that she drove it in traffic for half an hour with the Temp gauge maxed out. Good to know it lasted that long but to make a long story short we had the motor replaced and about 2,000 miles after that the transmission stuck in high (3rd I believe)(Automatic) gear. I thought it was a one time thing but it has happened 4 times now. The fluid level is fine but whenever the car warms up it sticks in high gear. When the car is cold it shifts like it should with no problems. Not being new to car problems I warmed the motor then drove it for about 4 miles and no problem, so it just seems as if it happens when the tranny gets hot. Any reasons why this is happening would be greatly appreciated!