it was all sand and I was digging in really hard trying to climb a hill. I talked to Robby about this as well, and since I am not the only one this has happen to under theses type conditions I think were going to call it the TCS maybe. I get what Doc has said and makes tons of sense but my tires were pretty level almost at normal drive angles and I have never heard anything remotely to this sound before even with all the off roading I have been doing but I have not ever sat there and spun my tires in this way either. So considering I'm in 4LO and might have been in second gear as well spinning the tires. This is what robby offered up.
At that moment, all free play within the differental is taken up, everything from the outer c/v of the slipping wheel, through the differental, and all the way to the outer c/v of the wheel with traction.
In theory, this shock load would ring the driveshafts and transfer case too......sounds like it was a mechanically violent moment.
Since I'm in WAG mode, if you had the wheels spinning fast enouph, and you did not have the trans in manual one position, it may have been in second and dropped back to first at that moment as well.....speculating on my part, but a possible scenario.
This made a lot of sense to me and is what I think happen considering it's not just me this has happen to in this scenario.