Front differential problems? on 2004 Buick Rainier

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?

Asked by for the 2004 Buick Rainier
was the transfer case empty? if it was, then damage has resulted and it needs serious attention. if not, look for hub bearing failure. it is much more common than the transfer case.