I bathed the diff in solvent, and then heated it with a torch to burn off the residual oil.

I used the Tig some, it worked fine but an awfully small bead, so I decided to try the MIG, and it worked fine BUT right after I welded where the side gears engage the spider gears each weld had a crack?

What am I doing wrong?

I routed out the cracks ( they werent deep) and Fused them back together with the TIG, but my confidence is gone now until I figure out what I was doing wrong or what was set wrong with teh machine/


a big Miller power source with a wire feeder mounted on top of it, using 308 stainless wire, maybe I should change to mild steel wire?

any ideas appreciated

I'm no pro but I would have to say using the stainless wire could be a source of the problem.

i have mig welded stainless to mild steel and had it crack just like you are saying. use some regular mild steel wire. or just tig it up completly with some mild steel rod.

I used 308 stainless to arc weld my diff with no preheat and it did not crack when I welded it. I just took it out after a summer of mud bogs and there are still no cracks anywhere. Don't know what to tell you?

I would say a lot of passes with the tig would be an option, I've never been fond of wire feeders for structural work like that, too easy to make a nice looking bead with no strength (yeah been there done that)

the TIG filler was 308 also, thats the part I really dont understand.

I guess Ill just bring it home and zap some 7018 rods on it.

I was trying to avoid all the slag and splatter, Ill try to tig it all firtst, if that doesnt go swell, Ill stick it I guess.

Im just curious why it cracked, ive welded lots of mild steel stuff wih that same wire and not had cracks.

oh well/

thanks for the replys, any other ideas?

i know what you are talking about. sometimes its just fine other times i have had it crack all over. just blast the shit out of it with 7018 on a good dc machine and roll.

MIG the shit out of all four corners of where the Spider gears mesh, front and back.

Like so...

Hey wnggrog,

did you read my post?

I DID MIG it, and it looks JUST like that (except I left in the cross pin, and I got a littel more filler in there)
BUt the welds have a hairline crack in each of them.

umm, but thanks for trying to help.

here is a way you might could help, what type of wire was used on that one?

Crank the mig up to 3/4 throttle on both dials and burn it in with plain jane wire, throw a couple 3/8" bolts into the crack and weld them in for insurance and you are done.

Try to make the beads convex, concave beads are more likely to crack, also if you can lay a wider bead with a little less penetration the bead is less likely to crack, especially below the surface. Also watch the interpass temperature.