Auto 4x4 works kinda like magic, you push a button and there is 4 wheel drive, push a button and back up and its gone. Amazing really...
I'm sorry I cuoldn't resist the temptation. I've had a long day at work dealing with very annoying people.
I actually have asked that question before. So like what is stated above, do a search for auto 4x4 or something to that nature and you should get gobs of information. Good luck with your search.