Front differental problems or 4X4 issues?

[Bonfire]

I have a 97 GMC 1500 extended cab. I have had very few problems with this truck other than the transmission being rebuilt about a year ago.
The problem started on my drive back home. The truck remained in 4 wheel drive for a few days with all the snow. I got on the highway in 2 wheel drive when a noise that sounded like metal grinding started. The sound winded down the slower the truck went when it came to a stop there was a clunk. I put the truck in park then shifted through the gears everything seemed ok. Got back on the freeway went fine for about a half hour same thing started pulled over in a lot looked under the truck everything checked out ok. I went through all the gears included 4hi and 4 low. It all shifted fine again and reverse worked good. I did notice when the noise started I was able to shift to 4hi and the noise stopped shift back to 2wheel and it started. If I cycled through 4hi and 4low back to 2wheel the sound stopped.
I had a flat also before I left for the trip and it repaired by Sears. The plug they put in came out and it slowly leaked over the course of a few days. Could the lower tire pressure of caused this? It was barley noticeable on the tire pressure. Could it be the 4 wheel drive no engaging properly?

[heavychevy85]

is it coming from one side or both my truck for instance did the same thing before diagnoseing the problem i found the bearing was out were the axle conected to the differential so check that out you should be able to grab the shaft and wiggle check both sides they should be pretty tight not loose at all so if you got play mor than lets say 1/16 then it prolly the bearing also might be the carrier bearing i had t replace all 3 bearings inside theres a 2 bearing set in side and a bearing for each side

[leolkfrm]

it sounds like the therm resistor in the front axle is not disengageing properly, it may be getting weak. worth taking a look at