Brandon; This isnt a computer problem, this is a plain old expensive mechanical problem of some sort.
Possibilities:
(1) A failed clutch. If the clutch disc fell apart, or the pressure plate broke somehow, the noise you hear should be coming from the bell housing area. I think this is the most likely failure from what you describe.
(2) A failed transmission: If you have a broken main shaft or some other internal component, the noise should be loudest in the transmission area.
(3) An internal transfer case failure. If something in the transfer case failed, the noise should be loudest in this area.
About all you can do with the vehicle assembled is to crawl under it while someone rund the truck and holds the brake on to see if you can isolate the area the noise is coming from (as long as you can do this safely). If you cant identify the failed component this way, then you may need to start removing the drivetrain components untill you find the source of the failure. For exapmple, if you can turn the front shaft of the transmission with it in gear, and the tail shaft does not turn, then you know the failure is inside the transmission.
I hope this is helpful; if so, clicking my accept button would be most appreciated! Thanks!
