agreed....
like edward said, sounds to me like a possible broken axle shaft or maybe some brake hardware issue, maybe.

The quickest way to check the axles is to just pull them out and see if one is broken or damaged in any way. It doesnt require any special tools to do... jack the wheels off the floor and block the truck up, remove the bolts around the axle flange on the hub... smack the flange with a hammer to get it to break loose... then pull the axle out. (in most cases this works) (in rare cases you may have to use a snatching tool to get the axle out if the flange is not made onto the axle shaft)

Once you do that and verify the axles, you've gone this far you may as well go ahead and pull the hubs too and check the brakes and hardware.