I have searched Google and CAFC for a solution to this specific issue. My 4WD Auto works exactly as it should. 2WD works exactly as it should. However, 4WD Hi and 4WD Lo do not work in spite of the dash button indicator lamps indicating that the selected mode is activated. I the snow, in 4WD Auto, when the back wheels spin, the front wheels will start pulling as they should. BUT, in 4 Hi or Lo, the front wheels never pull. The dealer put in 3 coder motors (so they say) and replaced the clutch pack (which did NOT need changed). After each "repair", they assured me it was "fixed". I didn't test is right away until the last time but, I'm sure it was NOT fixed any of those times. The last time, I insisted that the tech ride with me and I proved it still was not working. Apparently they were "testing" is on the lift with a computer. Ugh..... 
So, I have been wracking my brain trying to figure out why 4 Auto works and 4 Hi does not.
Has anyone else had and subsequently had this issue repaired? If so, what was the problem found? Is there any tech on these boards who can speak to this issue? I will be very grateful for any information. I love my Avalanche and don't want to give up on it yet. So far, the 4 Auto has gotten me through the south central PA winters but, it's disconcerting that the rear wheels have to spin a bit before the front start helping.
Thank you in advance,
Mike
So, I have been wracking my brain trying to figure out why 4 Auto works and 4 Hi does not.
Has anyone else had and subsequently had this issue repaired? If so, what was the problem found? Is there any tech on these boards who can speak to this issue? I will be very grateful for any information. I love my Avalanche and don't want to give up on it yet. So far, the 4 Auto has gotten me through the south central PA winters but, it's disconcerting that the rear wheels have to spin a bit before the front start helping.
Thank you in advance,
Mike