Rear end locked up

Back again, you guys were great help when I had my previous problem, I have another one. I have an '87 b2000 longbed with 42k on it someone gave me, I was driving on the highway and rear tire just locked up causing me to fishtale and slide to a stop on side of the highway. After the tow truck dropped the truck in my driveway I started it and tried to move it. It moved freely but makes a decent noise near middle of the bed to rear axle. I looked at rear brakes but they seem fine. Not sure where to start, thats where I need help. Would a bearing lock up the rear tires? If it did, would it still move? The way the trucks tires just locked up I would think the rear wheels wouldn't move when I got it home. Any ideas?

Is the rear differential okay? If the noise is coming from the middle I'd check the oil in it.

Would the rear diff unlock? The noise seems to be coming from middle to rear of the bed, but more middle. It is a long bed truck.

Thanks for the reply. I appreciate it.

Wow, this forum is a ghost town isn't it? Okay, mine's a longbed too and the drive shaft has a carrier bearing towards the middle of the truck. I don't know if that could seize and stop the wheels from turning. Besides, if the bearings were bad, they'd probably be screaming. Going back to your first post, was it 1 tire or both?