Driving down the road the truck engine will be running with no abnormal sounds, smells, leaks but will act as if not in gear. rpm's will rev but truck will not move. only after putting truck in park (lots of grinding noises) then pressing the 4wheel button then back to 2wheel (sometimes through two cycles) the truck will back into gear and operate properly. took it to a transmission shop put it on the diagnostic machine and no error codes were given to give reason why the transfer case disengages randomly. replaced the transfer switch per shop recommendation "just in case"it was okay for about a month then once again issues started again just the same as before.
I backed out of my driveway stopped my truck like always put it in d to drive heard a loud clunk noise and now i have 1 and 2 gear only to use the truck was stationary was on a main road i changed the transmission fluid screens filters everything flushed it out and still the same thing a lot of people are saying it's the sprag unit i have no idea what that is i have only hauled a few things with it when we were moving we only moved eight miles down the road used a trailer and the tow gear that is on the truck. also about a month before this happened the stability system light came on and said disabled but has not done it since also my truck is very clean always serviced according to the manual and is in very very good condition
Tl*the contact owns a 2006 chevrolet avalanche 1500. while driving 60 mph, the vehicle decelerated. the vehicle was taken to the dealer, but they could not duplicate the failure. the most recent failure occurred on february 25, 2008 while stopped at an intersection. the contact stated that the failure was intermittent; however, the stability light illuminated during the last failure. the vehicle will be taken back to the dealer for a diagnosis. the manufacturer was notified and the failure was escalated. the contact will receive a call back. the current mileage was 20,000 and failure mileage was 18,000.