It is rather important to know what alloy you are working with. Typically, cast Al have high Si contents. (Around 12%) This is so because at this composition of Si, Al has a very narrow solidification range, which reduces the chances of solidification related cracking. If you use the wrong filler, you will end up in a solidification range that is very wide. In this case, solidification related cracking will almost certainly occur, especially if you are considdering welding this under less than optimum conditions.

I believe you should decide how important it is for you to obtain a good weld. If it is important, then take the extra effort and cost and do it properly. If on the other hand you "have nothing to lose", then experiment away and don't be too dissapointed if it does not work out right.

Regards
Niekie Jooste

If you are going to have sucess welding on an axle housing, or any other aluminum casting that has been in similar service, regardless of the welding process, you have to find a way to get all the grease/oil out of the casting. The aluminum has many small pores that the oil gets into and will cause welding problems every time.

groberts is right. The only way to get this Aluminum clean enough to weld you will have to vapor degrease it. And if you don't forget it.
Sorry.

Hi there . I find that if you can prepare the joint/crack & pre-heat the aluminum to at least around 300 F. and weld it before the heat runs away,you will find that the filler metal flows in better- instead of turning into bird poop on top. If you pre-heat with the torch it also helps get rid of some of the oil etc. Just be careful not to get it too hot or You'll see a sudden disappearing act. Keep a short arc. W.S.

My son just read this and says he has heard of lots of dirt motorcycle cases being repaired with "J B Weld". If this isn't a structural thing maybe that will work. He says the statement "I always intended to get that welded but..." is often heard.

I bet most transmission repairers will have old cases that they will let you have for no more than scrap price. Then you could practice on that.

Good luck
Bill

I use an MG400 rod with a torch to repair aluminum castings but temp control is tricky and right size flame essential to achieve that control

its in the technique

this rod is engineered for DC+ or torch, and comes in sizes ranging from 3/32 (50-80Amp) to 5/32 (100-160A)

thickness and size of casting would hepl MG advise you 800-558-8524?

regards,
D