Spindle replacement or repair welding and rethreading is usually done on the bigger rigs, 18-wheeler stuff, etc. It involves some pretty specialized machining and welding procedures. On a 3/4 ton housing, it would probably be much less expensive to simply replace the housing. I've done a few emergency field repairs that involved tacking that nut into place, but only after getting a written waiver from the truck owner authorizing emergency fix. There's a huge amount of liability involved in that kind of a fix!
Jerry
