Sounds like someone overlooked greasing their U-joints. If your driveshaft smacked your t-case, I am sure that a U-joint failed on you. Friend of mine had to use my truck, and trailer to resque his son coming back from CA. That is exactly what happened to his son. Didn't grease the u-joints, and bammmmm, a ten dollar u-joint tore up t-case, and tranny. All because he didn't think to lube the thing. Oh well, it is a good learning experience if nothing else. U-joint was dry as a bone. I mean powder dry, rust in the pins, and oh my, what an easy cure.