Why can't a cracked differential carrier be repaired by welding?

[Brassplyer]

I've seen it stated that if there's a crack in the carrier, say from the edge of one of the access openings in the side, that it automatically makes the carrier junk, that the crack can't be welded. If you agree, why is this? If you disagree, why so?

Has anyone here successfully welded a cracked carrier and gotten good service out of it?

 

[rkj427]

Tip 1. Don't ever weld anything structural to your diff's center section. This is just a good rule because of the inconsistencies that are unavoidable when welding to any kind of nodular/ductile/cast/gray iron.

Tip 2. IF you do weld to it, even though I like 312 (super missile), the highest content nickel filler with the proper preheat and slow cool is the best measure in this case in order to minimize the troubles that will inevitably occur.