4 Wheel Drive/SUVs: 4-wheel drive wont lock in, linkage problem, vacuum lines

Question
cant figure out why wont the 4-wheel drive lock in when I need it to..on 1992 chevy truck c-1500

Answer
Johnny,

To give you a simple answer would be extremely hard without looking at the truck.  This problem, can be anything from a bad hub, to a blown transfer case, and could be as simple as a linkage problem.  Some of these rigs used a vacuum switch on the transfer case, which has vacuum lines that can be pulled loose, or the switch itself can be faulty.  
I would suggest that you purchase a repair manual, and try to trace out the front wheel drive section, starting with the front hubs.  A Chilton's or a Hayne's manual can be purchased at most auto parts stores for $20, and they have a lot of information on basic trouble shooting, and repairs.  These manuals are designed for a year or range of years for specific vehicles, and are invaluable if you are planning on doing any repairs yourself.

Carl