All it takes is one molten dingle ball to ruin your carrier bearings. A couple heavy layers of aluminum foil will go a long way in protecting your bearings and minimize any cleanup. You can use a MIG, TIG, or arc welder. We’ve welded the spider gears to the case in the past, but we just did it butch-style with no pre-heating or cooling cycle on the cast steel. If you know how to properly weld to cast steel, you probably don’t need any information from us on this subject. Keep in mind that you can weaken the carrier by welding on it, so if you don’t know what you’re doing it may be best to keep your welds on the steel spider gears only.