I am in need of some enlightenment.... My work truck is a '95 Chevy K2500, NV4500/NP241. I was in my work truck Monday, pulling a trailer. As I started to pull out into the highway, I came out on the clutch, and heard a loud popping noise, along with an awful grinding. Truck would not go forward or backward in any gear. My first thought was clutch, but depressing the pedal disengages and allows gear shifting. Just no pull when you release the clutch. Second thought was ring gear in rear end, but shifting transfer case into 4WD still would not pull. Got it towed home, and started pulling tranny next day. Can't find anything amiss in the transmission. Cant't find anything wrong with the transfer case. I have shifted the tranny through all 5 gears, and reverse. Using channel locks on front and rear shafts, I cannot make it slip. Transfer case works fine in all 4 positions by hand power. I'm wondering if there was some type of failure with the pressure plate/clutch assembly, but can't figure out why it will release to allow shifting, but then won't pull. Also, can't figure out what the metallic pop was, nor what the grinding was. Anybody ever heard of such a thing?

Suggested causes so far: faulty pressure plate, sheared key in tranny (can't find any sign), broken chain in transfer case (doesn't seem like it would affect 2WD),crankshaft broken right behind rear main (truck cranks and runs fine, just will not pull).

HELP!!!