You don't need to search, you just need to look... a few post's above this one. See all the stickies at the top of the page? yea, the threads that you passed to look at this one. The very first one is the "4x4 trouble shooting" thread.
Most 4x4 problems are no problem at all. Either a loose wire, or stuck shift motor. I've had my shift motor get stuck several dozen times. A slight tap with a wrench or hammer always gets it moving again.