Sounds like the front axle actuator is stuck on not disengaeing the axles fom the front driveshaft. If not that then the transfer case or controller has a fault in it. The actuator isnt very expensive.
PS There is a bulliten on the noise and I would mention that before you let anyone work on it and make sure that they know about it or are able to find it, may be covered under warranty. The Bulletin is GM #03-04-19-004B. You cold be having issues with what the bulletin explains along with something in the transfer case.
Thanks for the heads up.
All the best.