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.