I have a 2002 2500HD Duramax -While pulling a trailer a couple of weeks ago i noticed the transmission did not want to down shift while going up a hill. I stopped a red light and when I took off it slammed from 1st to 2nd and then would not go past 2nd. I tried several times and it would only shift between first and second. I stopped and shut it off for about 30 minutes and when I started back it shifted properly. When I had the codes checked the genius for got the numbers, something in the 700's and 800's (2 codes) talking about a stuck solenoid. Does anyone know what code or solenoid this could be talking about.