shifting problem
 

I just this 2002 duramax friday nice truck only has 69,700 miles it has a snow plow on it and that is the only thing that has been done to the truck. I took it out the saturday and pushed snow with it and about 2.5 hours into pushing it started acting up the transmission started sliping and when i got done with the lot and going down the road then now it wouldnt shitf out of second. Its really weird like a sensor or a wire maybe something of that nature because it dosent do it all the time and sometimes when it does it i can put it in neatural and back in drive it will be fine. just wondering if anyone had any ideals thanks

Hmmm So after you put it in neutral and back to drive it will go through all the gears fine??

no after we pushed snow for about an hour it was like it was slipping in reverse but then the service engine light came on and it would not shift out of second gear you could feel it shift from first to second then it would not come out of second after it cooled down it would do fine again but as soon as the tranny got warm again it would act up again. the next morning when i got in it the engine light was on but it was acting fine then the day after that when i got in it the light was out and it was fine but that was on my way back to the dealer ship where i bought the truck thank god they took it back after alittle bit of fighting with them. It kinda sucked tho i really like the truck. I posted this before they took it back and i really didnt think that they would take it back

my bet is a "limped" transmission. transmission goes into third gear and wont shift up or down and throws a CEL. this is from slipping clutches in the transmission.

any chips or power adders in its life? if it was purchased used at a dealer and someone previously had a tuner on it it is likely the transmission clutches got burned. most will reprogram it back to stock before trading it in at the dealer and one would never know there was an issue until a heavy load is put on the truck and it goes into limp mode

if so a tranny rebuild is needed