was driving my 79 2 wheel drive f250 through a grassy feild with some mud in it..when I got back on the highway I herd what sounded typical of haveing mud sling up under and make a thumping noise ..the noise kept up long after the mud was gone, and got worse. I pulled over and pulled on the wheel with my hands and their was some slop just a little so I took off the hub cap to inspect lug nuts..they were tight..the noise was so bad that I left truck over night in someones drive way..the next day I removed wheel bearings , cleaned them and repacked with new grease...wheel no longer had as much play but thump was still there ..cant be sure but looks like king pins are good. it goes straight down the road steering has no play. U joints are good ( jacked up both rear). ball joints are good. the knock is kind of a hard sound but not metal to metal .sounds like something is hitting the floor with a rubber hammer..I cant find it..left it roadside again tonight...last thought was possibly a broken strut?
Any guess you have will be appreciated..you can hear it at slow ( walkin) speed. and at 45 mph it sounds like damage could occour.

 

twas the other side....