Cool. You sort of gave me the answer I was looking for. I know about the welding rod numbers, but didn't know about mig wire. Basically, what you are saying is that either type, done correctly will be as strong as the normal steel we use (say 60KSI)

Personally, I use either 7018 or 6013. I like the feel of 6013, but it gets runny on me when welding vertical or overhead.

 

that's funny you made 14 bolt brackets cause I just made two sets last weekend as well. I used my bros online ordered brackets he used as a template that I drew out on thick construction paper and burnt them out of some 3/8 plate and punched them out on the iron worker . I made them for my buddies I figured what the hell it's easy enough. Guess what they worked too..LOL.

On the subject of welding from experience (I carry certified tickets for all position flux core and stick)I use a flux core Lincoln 71m for pretty much everything from welding shanks on excavator buckets,structural steel, and lighter stuff like 1/4 plate. Hard wire mig is not approved to be used on any of the big stuff I weld as it just doesn't have the same strength and ductility as a gas flux core wire. Gasless flux core is even more a no no but can be strong if you use the correct settings. From school I remember you could run it hot and it would look like a million bucks. Its just when it was bent in a plate test it would crack everytime unless dialed in just right.
Hard wire mig has it's place for smaller material 1/4 and down. We use it for welding handrails mainly.
Now a 7018 rod is equivilent to flux core 71 m anyday. Mostly used in the feild because it is always clean and wont get porosity in the wind like wire and will even burn through most painted surfaces making it ultimate for versatility,portability, strength, but slow. I welded all day today on a new hospital job with stick today and all overhead....good times.
See what I do on my truck for anything critical and needed to be strong like spring perches and bumpers I tack it up with my 110 gasless buzz box and fully weld it with stick when I bring one of my shops rigs home or rent a good stick machine for the weekend which is exactly what I did tonite so I can weld on my new front and rear winch mounts, and bros 14 bolt spring perches. I think the 14 bolt is cast iron so I might have to use a high nickel rod for that.
Hey 75f350 is it just the pot that is cast on the 14 bolts or the tubes as well. I'm sure you've welded on yours....

 

The key thing here is ductility! The ability to bend and not crack. Try welding a tack with a gasless wire or 6013 and bend it off. It will snap. Now compare this to a flux core or 7018 and it will bend back and fourth then break off. Much nicer to use when fabricating as well because you can bump it around and munipulate it. I hate my gasless buzz box when you just need to nudge a tack and it breaks off. This is why it's used on stuctural and steel boats. O by the way 6013 is usuallyu used for sheet metal or 1/8.

 

I believe this to be Nodular Iron. I could be wrong, but this is what I was under the impression that it was.
I have welded with 7018 using a pre/post heat method, and have had success, and I have tig welded them with Stainless filler, and I have used my millermatic mig.
The mig required quite a bit of pre heat. I had to really get it hot, and make a few passes, but this worked fine and I have had no problems with the tubes. The tubes are sort of a weak link on the 14B, but some welding usually makes easy work of this. Peening the welded area is probaly as important as the pre heat and post heat. Be sure to relieve the stress as the stresses will be different between the two types of metals.
Depending on which axle you have, the perches might be cast iron, so high nickel cant hurt there too.

 

73--Thanks for all the info! I just learned a lot in 2 posts.

 

I am insanely jealous of your shop.

Great fab work on everything too.

I was thinking though, what is it you do that requires that big of a diff cover. Hahaha. That thing is massive. Probably bomb proof.

 

so at least I'm not the only one who hits the shop when I am bored...

How are the later run of 14b brackets looking? That is if you got to them before that cold knocked you out of commission...