I have the same truck....If you ever see your 4x4 switch on the dash sitting in neutral (red light) and it is fussy changing from 4auto to 4x4 then back, the switches on the dash do not last. 5 minutes to replace but I leave mine in 2wd. It will switch on its own at times and do some weird stuff. I am on my second switch waiting to find a replacement beside GM. Any ideas anyone?