A friend of mine back home is having trouble with her truck.its an 02 Avalanche with push button 4wd. Im still deployed so Im tryin to help her from here so she wont be lied to at a shop or anything.

The truck is stuck in 4hi. she has tried to get it into 2wd and 4lo but nothing... She said she can hear somthing under the truck (Im assuming the transfer case) attempting to disengage the 4wd but it never actually does it..so Ive ruled out the possibility of bad switches..any other ideas?