Not sure if i posted this in the right place but.. My 2001 5.3 Z71 offroad automatic trans. isnt shifting. I have to manual shift it and it only goes into second and third but after my speed gets up it will go into od i think. It doesnt downshift, well it doesnt shift at all. I can put it in first but it only goes in second.. in other words i can start off with the shifter in first gear position and shift it to second and nothin changes but when i go from second to third it shifts.. Any and all help/advise is greatly appreciated