If you've got a CAD, I would do this:
-turn on the truck (engine should be on for this test to assure vacuum is available for CAD operation),
-shift into 4wd high,
-drive like 20 feet just to be sure everything has moved into place (t-case and CAD collar),
-block a tire and put truck in park if auto or shift into neutral for manuals,
-jack up front/passenger side tire and try to spin it.
If the CAD and t-case work properly, then that front tire shouldn't spin. If it moves, then try to rotate the front driveshaft. If the t-case works properly, then the front driveshaft won't move.