so... having had a little fun before, I figured it test out the fresh A/T rubber on the Tahoe today... just a little, with my 3.5yo boy. One hill, one measly quick hill, nothing crazy. Mind you the truck has been inspected by experienced mechanics and given the “all good” for operational 4wd. Got halfway up a sandy hill... and lost momentum... backed down, always climb things with gravity in mind to get me out. Tried a second time. And went to reverse, got stuck. 45 min of digging and pulling out all the tricks in the book to get out. I then realized the front wheels were not spinning or digging... hence the rear end getting beached on sand. No warning or trouble messages... 4wd light on, clunk into 4wd low... but not spinning. 4.5 hours until recovery arrived, due to one canceling before they even arrived. Long and short of it, replaced the 4wd actuator, $75 from auto zone and $8 for the lift and stall usage. 4wd now working no problem, tested on lift. Was able to complete it same day and still have time to get a case of beer to celebrate the day.