heres how to do it proberly!!

the main problem with welding (thats if it doesnt break which is very likely) is distortion, the little side gears which hold the axle splines are now fixed rigid and the weld pulls them not perpindicular to the axle and under high load this helps to tear the end off the axle then its a real bitch get the broken piece out too!

the hemisphere also distorts and the crownwheel then has fully variable backlash at different points around the gear so its wears badly, the bearings get some bad loads too

the way to weld it is to pull out the little spider gears and shaft, cut a little piece of pipe about 40mm diameter and carefully grind it so you have to bang it in with a hahmmer to push the side gears out as hard as posable then weld everything up evenly, but its still dodgy as all hell

then if you do break an axle just take the axle out of the other side and pop the broken piece out with a long rod and drop in a new one

the best way is to cast the centre with aluminium (with the little pipe in the centre) that way there is no distortion

i used to have a little side line doing this called Arrow diffs, i have done hundreds and never had one break