What are the tricks to weld craked differential in the bush

Frank, I have had this problem on many occasions. The company in Newman that service the mineing equiptment charged me for a spray can of electronic degreaser/cleaner. On quizzing them they said it cleans the weld site and penetrates the crack cleaning it without leaving any residue. The process is:1. Empty the diff. 2. clean area with wire brush,then de-greaser then water. 3. Grind a "v" in the crack and beyond slightly. 4. Spray liberally with electronic cleaner (available from "Richard" Smith stores) getting as much pressure into the crack as possible. Weld using three batteries in series using 3.25mm general purpose rods or weld-all rods. If you want to check for cracks, mix some flurocene with water and apply to the surface. the crack will appear a different colour when you look at it in a shaded situation. Carry some electronic cleaner with you as the average farmer doesn't have any. It's good for cleaning lots of things. Mal Try.

Frank, Mal is spot on with his advice to you but I would like to add some more info. Firstly, after completing the weld, weld a small circle at the end of each weld. This will reduce the likelihood of the crack extending after being repaired. Secondly, when I used to do this as part of my job, you could often get away with this type of repair without any form of surface cleaning at all if you used the correct welding rod (I've even heard of guys welding the housing with the oil still inside, though I wouldn't advise it). A visit to CIG and they should be able to help you with which rod to use. And lastly, you can buy crack testing kits from any major bearing company or industrial hardware. Hope this helps.
Derek.