After doing some searching and reading. Let me see if I have a decent understanding of this. The Knuckles on a housing (Dana 44 or Dana 60 the inner "c" that is welded to the tube) are Forged Steel, and these can be welded onto just like normal, as in no preheating, just mig weld or stick weld.

The center chunk is cast iron? Or is it also Forged Steel? This needs to be pre heated to weld on. Like if you wanted to add some 4 link tabs to the top of it out of mild steel, you would need to clean and pre heat it to get good solid welds and you would need high nickle rods for the best welding.

Is any of this right, please post away with whatever I missed or got wrong. Any chance of putting up a sticky post or a welding tips post that would include some of this infomation for everybody.

Thanks
Depdog

You're on the right track as far as the inner knuckles go onto the tube.
As for the center, on a Dana, it's not forged steel. There seems to be a debate over whether it's cast iron or cast steel. I think it's cast steel.
As for welding on it, a TIG works well too.
If it where me though, I'd add a truss tube and weld the link ears onto that. (That's just me and my .02)

It would be best not to weld to cast iron in applications where high tensile strenght is important. If you have no other choice, the way we were taught to do it was to lay in two rows of closely-spaced stud pins on either side of the weldment and then filet weld both sides right over the studs. It is a PITA, but it will be as strong as the base metal.

th way I was taught to weld cast iron was to do it like a millwright would. they drill small holes all around the crack that needs to be fixed and then weld over the holes giving the weld something to penetrate and hold on to.

-Scott

I preheat the C's and use a mig. I preheat the center sections to 450 deg. and use a mig. Nickle rod might be better, but I haven't seen any problems from using plain steel wire.