We have a tandem axle dump truck at work that has a crack in the rear diff housing (cast). It's a 6"-8" crack across the top of the housing (think 11 - 1 o' clock on a clock). And it's leaking oil to the outside. I've welded some cast before but nothing this big or that needed to be water tight or rather oil tight. I figured I will relief holes at each end of the crack, vee it out and pre-heat. My welding approach is where I'm hesitant. I'd like to weld it in a continuous pass to make sure it seals up but am not sure if that will get too hot. I had an old timer tell me before to back step cast an inch at a time but I think all the starts and stops will not seal up correctly. I've got some NI-99 electrode I've used before with good success. I also have some NI-99 filler but have never tig welded cast before. The cool down is the next obstacle. It's a big axle (20000 lb. GAWR). And it's still in the truck and they're not taking it out/apart. I can probably round up a handful of welding blankets and try to wrap it up. Thoughts? Suggestions?
