[LONGHAIR]

Don't do it. IMHO it is never done "properly".....even if I thought there was a proper way. Most of the time this is done with the differential in the housing, which IMHO is totally wrong to start with....The metals involved are not really compatable for welding together, things are never cleaned well enough, etc...and many time the stock axles are used. None of this is safe. If you have any power at all, you will break something...and if you don't why bother?

Spools are cheap....if you even really need a fully locked axle anyway, but aftermarket axles are a must with them too. Completely locked rear axles are rather rough to drive, it wants to push you in a straight line, no matter how you turn the wheels. Fronts are even worse...mud bogging and truck pulling are really the only applications for that and like powerdriver58 said, those guys un-lock most of the time too.

I have seen welded diffs fail in sand racing...and the results are ugly. I saw a jeep drive completely over the christmas tree (and nearly a few people) because of a weld failure......I am totally against them in all applications.