[hpfiend]

Hey all-

Looking to weld a ford 8.8 differential cast iron center section to the pressed in mild steel axle tubes. I have read some people use a nickel smaw rod and some tig weld it using nickel filler? preheat with torch or not necessary?

I have a Thermal Arc 185 tig/stick setup and a larger Lincoln tombstone arc welder and an oxy acetylene setup.

Thanks,
Andrew

 

[S obsessed]

That guy seems to not mind what you do. It is nodular iron but must have a fairly low carbon content or something. I have tigged with 309, migged using a cooler setting and a slow weave with er70s6, nickel 55, and brazed with both tig and silicon bronze as well as brass and gas. Best option is nickel rod and make 1" beads and peen with hammer. Keep everything cool or else you may distort the tubes. In this type of joint the cast part doesn't pull away and crack like it would if were a butt joint, it seems to stretch the weld and if kept cool it doesn't seem to bother. Take weight off axle so when you weld it doesn't try to bend on you.

 

[rancher76]

I have had good luck using supermissle weld or MG super 600 SMAW electrodes and running short beads and peening as described above.

 

[hpfiend]

for clarification you have migged with nickel 55 or tigged? How did you clean it as it looks very porous? Does nodular iron heat up uniformly like mild steel or more like the surface of a sponge with cast iron?

I am very tempted as I already have the welder but am intimidated by what I have read and don't want to ruin the differential- I have found a guy that will do it for 125. I can tig mild steel really well and aluminum decently. stainless somewhere in between. I have been to lincoln welding school and taken the basic tig training there but am definitely not a pro...

I think the mg super stick welding would be better as it is soo rusty/grimey/porous but I am much more confident with tig than smaw...

 

[B_C]

Since you need the rear end and most likely will never do this job again just pay the pro and rest assured your rear end is happy......125 bucks doesn't sound unreasonably.....How much is a new differential? Last time I checked Ni rod 99 was 45.00 a lb. and I only use it twice a year......

 

[S obsessed]

I agree with BC, you woupd be better off having them do it and seeing how its done, cheap education if you will. To answer your questions though, mig was with er70s6 wire, tig was with 309L. I have knocked flux off of nickel rod and sanded smooth to use with tig but wasn't pleased with results so I am thinking there are some additives in the flux that helps out. The nodular iron is sponge like in appearance but don't be fooled as no cast iron is really porous like that, its just from the mold its cast in. There can and usually are some voids in places from air pockets while casting but thats to be expected. Once you grind it clean you will see it looks like steel. When you grind the iron you shouldn't use anything that might imbed into surface so stick to sanding discs or flap wheels then maybe run over it with a carbide bit. The prep work on cast iron can make or break it.

 

[hpfiend]

Thanks guys- call me adventurous but if I were to try it with some nickel 55 filler and it should crack or turn out badly- I can still have the guy grind it down and weld again as long as he uses the same filler, correct?

 

[con_fuse9]

The 8.8s are cast steel. People weld to them all the time. ER70-6 and have at it.

You can do a spark test to confirm.

The 8.8 is used on lots of jeeps as a cheap axle (taken from Mid 80s broncos). There are a couple of web pages out there that talk about welding trusses and suspension mounts on the 8.8.

Spinning the axle tubes is a problem with the 8.8 (and the Dana 44). Everyone just runs a bead once around (I would tack weld and do it in at least 4 sections, alternating sides - maybe even 8 sections).

I talked to Balistic Fabrications which make "shave kits" where you cut out a piece of the differential for better ground clearance (GM 14 bolt axles are a beast!) and they told me they MIG weld with ER70-6. Both for Dana 60s and GM 14.

I'd probably just MIG it, but 309 filler has a lot of Nickel in it. Also consider MG 600 or any of the stuff called "Super Missile Rod" High nickel chromium, good for welding dissimilar metals, pretty much zero chance of cracking.

Personally I would take diff out. The diff actually puts sideways pressure on the housing (pre-loads the tappered bearings) and putting a lot of heat in the wrong/right area and you could loose some of that pre-load. Measure the back lash first. Reinstall, set the drag torque, and double check the backlash when you are done. Very critical to get the same backlash when you put it all together. Everything else has a bit more 'slop' to it (allowable variations)

BTW, their are people who weld on similar housings and do everything from pre-heat to peening but i haven't found anyone yet that said the just MIG'd the tubes and it failed after a while.

 

[Awelderiam]

Thanks guys- call me adventurous but if I were to try it with some nickel 55 filler and it should crack or turn out badly- I can still have the guy grind it down and weld again as long as he uses the same filler, correct?

This is from me.....if someone brings me a piece that they have "played" with its a little higher than without the extra prep work.......take it to the pro.....its only going to hold up your car......

 

[BlueArc]

Spinning the axle tubes is a problem with the 8.8 (and the Dana 44). Everyone just runs a bead once around (I would tack weld and do it in at least 4 sections, alternating sides - maybe even 8 sections).

That's what I did. I welded my 8.8 up a few years ago when I had it apart. I set it up straight on my bench, put four good tacks on each tube and welded around with the mig welder. Can't remember if I pre-heated at all.

A number of years and 100+ passes pulling 1.5-1.7 60's and she's still doing fine.

 

[brucer]

I've mig welded about 6 of these rearends with er70s-6, they weld pretty good..
I clean with a braided wire wheel and acetone, tack weld around the tube then I stitch weld alternating sides as I go..

 

[hpfiend]

Thanks for the replies!

I spoke with the pro and he said go ahead and try it and he can fix it if I get stuck... how can you beat that!

Plan on removing cover, axles, carrier, wheel bearings and seals and try to get as much grease out of it I can. Going to leave carrier bearing races but there is a lot of metal between them and the outside surface and I plan to go short distances rather quickly.

Going to prep with grinding wheel all the way into corner joint, clean up with flapper wheel/wire brush and acetone, blow dry with air gun.

I am going to preheat to 400 with temp crayon and OA torch, use Ni-55 tig filler, tack 4 places on each side, weld ~1.25" section on one side peen with 3 lb hammer and some sort of dull punch and wrap with fiberglass, then 1.25" on other side peen and wrap with fiberglass and allow to cool to touch, turn over and do the same on opposite side, for a total of 8 times until I am all the way around.

How did you guys hold the rear end? I don't think we have a bench that big that can hold 330 lbs or so... I am thinking of putting a pallet over the tines of our front loader tractor and blocking the axle tubes to keep it level and then lower the tractor bucket to seat height to use the pedal seated or standing as I dont have a hand control yet.

I will post pictures when complete or update with ignominy when I take it to the pro.