Thanks, although everyone i've spoken to seems to think that's not an option. I'll have to hunt out someone who specialises in jeeps i think.
Horsepuckey! Drain the diff and clean it out well, if you use brake cleaner, make sure it's all evaporated before you start welding. Use the brake backing plates as a guide to line the tube back up with the other one and smack it back in place with a sledge and block of wood, rotate as needed.
Spray down the end of the tube with a solvent and compressed air to get it as clean as possible and then remove all the paint as far into the crack where the tube meets the casting as possible. Also do the same where the original plug welds that held the tube in are.
Take a cutting torch and use it to clean out the crack as well. If you hit the Oxygen cut lever before the metal is hot enough to oxidize and cut, it will just clean out the paint from deep in the crevice.
Once you get it shiny clean, no paint, no oil, no dirt and the tube lined back up, run a Mig pass around the tube to the diff and then re-burn in the plug welds. If you wish, you can use the torch to warm up the weld area slightly to drive out moisture from the cast diff section.
If you do it this way, it will be fine.
Back inside the diff, run a bead of silicone and wipe it around the juncture where the tube ends inside the diff. That will stop oil from weeping out the tube.
At the end of the day, we're talking a couple of hours to save a diff housing. Even if it fails to stop the leak, that's all you've lost.