Probably a bad axle u-joint.

 

well found the problem not front but rear inner left tire was blown out but thay are not 6 weeks old so got anew one for free

 

Mine was the one with the full-loc clunks in eiither direction. (no rattle) Have yet to find anything cracked or loose. My brother had a '84 3/4 ton 2WD, put over 200K on the thing. He told me his had the same full-loc clunk from the time he purchased it. Weird.

 

Mine does that too. I hate it. It almost seems like a geometry issue with the ball joints, like they are going over center and binding a bit or semething.

 

The 4x4 king pin dana 60 front ends can get the death wobbles too. I had to rebuild mine.

My frame cracked bad at the steering box. I eliminated the brackets and mounted the box directly to the frame, 3 weld/patch jobs all failed before i finally scabbed a long piece of 1/2" plate to that section to the frame. No cracking since then.