I have a 2004 Rainier with AWD/5.3L V-8 and when I reach 25-30 mph there is a humming like sound that almost sounds like the tranny is stuck. I filled my AWD transfer case and the noise is still there, could this be the front differential. One other thing in a blizzard 12/24/09 i got stuck several times and the AWD ligth came on but went off when the care was restarted and has not come on again. That's why I filled the transfer case but I am not sure what is going on now. Any ideas?