Search the sight there are several threads that talk in depth about the front diff and issues that can cause loss of 4wd. If the AWD icon stays on in the cluster when its in reverse I would start by changing fluid to see if it is contaminated. If this doesnt help you will have to dig deeper (cracked sprague carrier, bent armature plate, etc) but first read up on the diff and the AWD system and how it works. good luck...