pmacks replied:

Hi Wayne,

This may help, next time you are a TJM kings park take a walk down to the end of the driveway and ask Brightweld to have a look at it they are brilliant, and specialist welders and fabricators and do a lot of work on tucks ect, not doubting your welding skills but these guys are brilliant.
As always dont work there, just a happy customer.
pmacks

davidta replied:

Hi
First of all, let me say that I may be completely wrong.
To MIG a diff, you would need to grind a new seam a few mm either side of the crack, heat the area around the crack till it is red hot before welding.
Or use an arc welder with Ni-Cad or Certanium rods.
Hope this helps.

Kiwi Ray replied:

Try Low Hi rods on Negative pollarity, your prep work will need to be good and grind out at least 30 mm at each end of the cracked area if you can
Ray

Member - Tony G (ACT) replied:

G'day Wayne, I went through the same on my 47 Troopie, repaired it three times all with an arc welder. The problem is that a small amount of oil is in the crack and the weld ends up honeycombed, although it looks ok.

The only way is to replace the diff housing with another one. Try Central Coast wreckers for a replacement.

Truckster (Vic) replied:

Wait for Andrew (awill4x4) to find this. He will let u know

IMHO, replace it.

rooscoota replied:

hey hey g'day

would be inclined to agree with the replace the diff housing scenario as you'll never get the two welding surfaces clean enough to get a full and decent weld happenin'.... there will always be diff oil residue there that you will not get out no matter how thorough you clean, the weld will always be pourus and will leak.

regards
____________________________________________________________________

lifes a garden.... dig it

Member - Doug T (QLD) replied:

Hi Wayne
Ive never looked for cracks on mine 94 model , was wondering was it front or rear diff as i will have a look , I saw a Patrol at Wolfe Creek Crater that had the front housing collapse on the Tanami and he had it welded at the granites to get him by , but then again I think it depends on how one drives on really bad rough roads, over the years Ive tried different methods but every road needs a different approach, 1967 in North West Australia in the old EK Holden I found it better to get up to 55 MPH and took the corrugations day after day ,but now with my 4x4 i'm happy to sit in 1st 2nd 0r 3rd gear all day if need be and hopefully I won't have any problems. Hope you can get fixed without too much cost .

Doug

awill4x4 replied:

Wayne for a start Mig welding is fine, the diffs are all welded by the Mig process from new anyway. Whether your Mig has enough power I don't know as you didn't tell us what machine you used. Are you using a Mig with shielding gas or are you using gasless wire, if gasless wire I think you will be pushing the proverbial shiat uphill.
For a start I would find the ends of the cracks and drill a small hole at either end, 4mm diameter will be fine. When a crack is present it will lengthen as you weld it and you won't even know and although you may have ground out the crack it will continue moving past the ground out area. When a hole is drilled the crack will stop there.
Between the drilled holes then grind a groove and then wire brush and clean out the groove. Unfortunately diff oil is a terrible contaminant and you must really try to remove it so wipe the groove down with lots of Acetone or Methylated Spirits. Some guys like thinners but I find it leaves an oily residue which can contaminate a weld. When you've used the Acetone/Metho and it the welds are overhead it can pay to use compressed air to blow any residual out of the groove prior to welding.
Depending on whether you are working overhead it pays to put in a hot and fast sealing weld then wire brush back and then a capping run to finish off.
One thing to remember is the welders mantra "clean, clean and clean again" I can't over emphasise this point.
Hope this helps. Regards Andrew.

Mudness replied:

G'day Wayne, shouldn't be a problem. Drain the oil, grind a weld prep nice and deep into the crack (a bit past each end) get the oxy and preheat to burn out any oil residue, and mig/ stick up (you need good penetration). If the cracks are right at the bottom where it may be impossible to burn out the oil residue (oil will keep running down in to them) you may have to remove the diff and roll it over before preheating. If you are not confident welding then get someone who is to do it. Over the years I have sucessfully fixed many cracked diff housings and hydraulic cylinders this way.

Member - Doug T (QLD) replied:

That might work ok if it's only small Wayne, as long it don't weaken it at the welds.Geez didn't I cause a outcry from a few self proclaimed engineers when I done 3 spot welds on my Axle flange after I sheered the 6 studs when the auto locker gave a big kick but i really do think they must have been very loose at the time and maybe 3 or 4 nuts were gone altogether because I could not find them on the street,Oh they reackoned i was gonna get killed or kill someone else when it failed , well it's been into the SD and working hard over dunes at Easter and i did get 3 or 4 small clicks in the rear one but I reackon when in 4wd a lot of stress is taken from the rear and shared with the front so I had no troubles, I was going to replace it with an ARB air but it seems to be going ok so far now .

Doug

Richard Kovac replied:

Wayne

You must remember that you are welding cast steel to formed steel I would requirement LH rods or the same in MIG eg. wire and gas

Most mig,s sold run wire and gas the same as GP rod,s

As said above you have got to get rid of the oil

And pre heat the weld area (not to RED HOT as above)

Good luck

Richard

Hems replied:

Hi Wayne,
Once you've finished the welding and before you paint it and put it back into the vehicle, you might want to have a magnetic particle inspection done on the weld. Won't cost you much ($50 - 75, might not even charge you if its a simple job) but it will tell you if your weld has cracked. You will then have peace of mind instead of filling the diff back up, re-installing the axle, suspension etc... and have an oil leak straight away. If you find any further cracking its easier to go back, grind out reweld and re-inspected until you get them all. The inspection equip is portable (240v electromagnet and 2 aerosol cans) and takes a couple of minutes provided the area of weld is free of paint. You'll find the people you need in the yellow pages under inspection services or non-destructive testing. Some companies are CCI Pope, ETRS or M-Test
Regards
Glen

DesC replied:

anything that i usually repair that holds fuel or oil i use a stick welder as a mig weld is porous to a certain degree. Every fuel tank and diff housing that i have had crack up & repaired by a boilermaker he has stick welded it. 16 years ago we had some bridge building contractors get us to weld up some reo for the concrete and would not let us use migs, so we used a stick for 3 weeks. They said that the mig welds rust out in the concrete way before a stick weld. They were pretty big contractors (Costains or Theiss i think) but maybe just being over cautious. We just did what we were told. I have tried the MIG like you have and the job always leaked or weeped.