It is one thing to weld a crack in the housing but I don't even see that as the main problem as bad as it is. Yes I imagine you could weld the crack in the housing itself and I imagine it would last a good long while. I see a bigger problem with the actual threaded part that the plug screws into. It is obvious from the picture that when it cracked the threaded portion separated by a good bit. A weld will fill the gap but the diameter is now larger than it originally was. It is highly unlikely that the drain plug will seal it properly because of the larger thread diameter now. And I doubt that another bolt will work unless it is drilled out and tapped after the weld and even then I would be suspicious. I agree with the general consensus that the housing has to be replaced. If it was me every time I drove the thing I would be looking under the vehicle to check for leaks. Best of luck..