Cast Iron Differential Weld

[jb1390]

I have an AAM 11.5 in my duramax pickup. I've been sled pulling some recently, and want to beef things up before something breaks. One rare, but possible failure is spinning the center section around the axle tubes. They are held together with some plug welds and a press fit from the factory. Many people weld the tubes (steel) to the center section (cast), all the way around. I have a spare differential casing at home - and tried some tests with MIG and er70s-6. Without preheat it ended pretty badly like expected, might as well have been glass. With preheat, it was tolerable but still pretty weak.

I got a stick clamp for my TIG welder, and some nickel rod, which had some pretty promising results, even before preheat. That being said, I'm new and not very good at stick - it's difficult for me to distinguish between the moving flux and the weld puddle. With MIG, the puddle is all that's there. I found online today that I can get a pound of nickel wire for around $70, and I think the results will be visually more appealing if I stay with MIG as opposed to trying to make it look nice with stick without much practice.

I found a chart online that said use 100% argon - which I have for the tig. Any thoughts/suggestions?

 

[muddstopper]

As someone that has spun the axle tubes a time or two. I welded mine up using 7018 and never had a problem with the center section cracking. This was on 12bolt chevy truck rearends, but I dont see why it wouldnt work with the new truck rear ends. We used to weld up the tubes on dirt track cars too.. Cant remember every spinning a center section or cracking the housing after welding one. You can try preheating the center section and using post heat as well as preheat. Normal preheat for mild steel is around 400-600 degrees f. For cast, you will need to bump up the heat to around 800*f. Also, try welding just a inch at a time and skipping around. Ping each weld after welding to help relieve the stresses. I like to use a needle scaler to ping with, it removes the flux and pings the weld at the same time.

 

[jb1390]

As someone that has spun the axle tubes a time or two. I welded mine up using 7018 and never had a problem with the center section cracking. This was on 12bolt chevy truck rearends, but I dont see why it wouldnt work with the new truck rear ends. We used to weld up the tubes on dirt track cars too.. Cant remember every spinning a center section or cracking the housing after welding one. You can try preheating the center section and using post heat as well as preheat. Normal preheat for mild steel is around 400-600 degrees f. For cast, you will need to bump up the heat to around 800*f. Also, try welding just a inch at a time and skipping around. Ping each weld after welding to help relieve the stresses. I like to use a needle scaler to ping with, it removes the flux and pings the weld at the same time.

I was hoping to avoid a preheat anywhere above about 200. I'm fine with draining the oil, but really really don't want to pull the gears and bearings out.

I guess some differentials have cast steel vs cast iron center - cast steel will tolerate 7018 or mig welding much better than iron (which is what I have). Based on my tests welds, preheat to 250 or so was tolerable with er70s-6, but nowhere near as strong as the nickel with no preheat.

 

[Shield Arc]

Here is some really good information on welding cast iron.
4437 Prospect Rd ,Whiteford ,Md 21160
Cast Iron Welding - Turlock, CA - LOCK-N-STITCH Inc.
Cast Iron Flux and Filler Metals for Gas or TIG welding
Stick Electrodes - Welding Cast Iron

 

[CNC Dan]

.....Ping each weld after welding to help relieve the stresses. I like to use a needle scaler to ping with, it removes the flux and pings the weld at the same time.

It's peen, not ping. As in "ball peen hammer".

And yes, a good way to relieve stress in a weld as it cools.

 

[jwmorris]

Cast iron is different than cast steel, I don't know what you have though.

On cast steel you can weld it much the same as regular steel. With cast iron to steel I use silicon bronze and a TIG.

 

[yomax4]

Both materials respond well with 312 stainless. I have done this process as well and we always used Super Missile Weld or MG 600 or plain 312LHS or LSI. 120K tensile to boot. 7018 -8018-9018-11018 all should be ok too but 11018 will have a little less ductility that 312. Good Luck..

 

[flusher]

I used Super Missile Weld (1/8" rod, 130 amps, DC+) to weld a broken flange off the lower right side of my Farmall Cub engine block. No preheat. Used skip welds about 1" long, kept the temperature near the weld site below 300F (used an IR thermometer) and let the block and flange cool to around 100F before welding the next bead. Peened the beads while cooling with an air hammer using a pointed chisel. It's slow going, but the resulting welds were strong.