truck stuck in 3rd gear in 2000 silverado
 

so I swapped a 6.0 in my 2000 silverado and got the transmission rebuilt during the swap as well once I got everything together the problems I had was it starting in the wrong gear. It would sputter when I took off till I got to higher speeds then it would run fine. Its throwing a 2-3 code in the transmission and torque converter code. any ideas???

Take that sucker back to whoever rebuilt and get them to take care of it. I had that problem in my old dodge of starting in like 3rd gear and stuff and it ended being something the transmission rebuild did