Yep, this. ^^^^^^
Four wheel drive hubs have come a long way since the first auto lock hubs, which were somewhat troublesome. My 1983 K30 had auto locks from the factory, and like a box of chocolates, you never knew what you would get when you shifted in and out of 4wd. Those early one like that were the ones that had a little spring clutch setup in them, and you drove either forward or backward after shifting them to engage them. When disengaging, you shifted, then drove the opposite direction to unlock them. This is where the problems usually happened, and one or both would not un lock. If just a little bit of the wrong grease got in the wrong place, the hub would stick, and not unlock. The newer autos are pretty reliable, and most use a vacuum to engage. The manual position will override the auto in the event the auto fails. My last three trucks had these, and they have always worked. The older ones are easily converted to manual hubs, and it is well worth it.