2004 Ford F-150 4 Wheel drive

If you can, support the vehicle on all four corners with some jack stands. Or if you have access to a lift that's better. Get all the wheels off the ground and start the vehicle. If you have someone who can sit in the truck while you inspect it, it is much safer. Engage the truck into 4x4 and watch the front half shafts. If you have a broken hublock one of the axles will be spinning and the other not. Since most things choose the path of least resistance, the halfshaft spinning will be the hublock that is broken. If you need any other help, or if neither shaft spins, post back and we'll go from there to get this figured out.