Hi All, I have a 1980 custom deluxe that I drove regularly for a few years when one night the rear end just locked up going about 30 MPH. I tried to go forward after stopping and the truck tried to go forward, but wouldn't. After a while I tried reverse and it worked. After that it went forward ok and I was able to get home. The thing is the truck makes a clanking sound after reaching ~20 MPH. I pulled the diff apart and the gears all looked good. There was one single sliver of metal about the size of a thumb nail. All seemed good. I put it back together and it still makes this noise around 20 MPH. Drive line doesn't seem to have play. I put it on jack stands and accelerated till it makes the noise but I can't figure out where its coming from. Any ideas? This is nothing I have experienced before. Thanks for any help.