[reno911]

Ring and pinion gear, something along that line. Or a ridiculously seized bearing. I haven't taken apart the diffs on either of my 2 4x4s but I can't imagine it being hard to access the diffs. If the spider gears failed you should still be able to turn the ring and pinion.

You could have bent the front stubs so bad that that part of the drive line has seized, but this would be noticeable with tire wobble.

Do you have any aftermarket parts in that area? If you used a longer screw you could have went through into the diff housing causing it to seize.

Thats all I got!