cast iron welding

[whitey82nd]

I have a crack in my transmission. I have tried to weld transmissions before with not much success. Can anyone give me some advice on the procedure and specific amp settings and rod selection for this process?

[JWELD]

What type of Tranny is it, Aluminum or Cast??

[MAC702]

You have at least two things working against you on this one. First, it is cast. For this I would recommend Ni99 rod, a very high Nickel content which flows into the casting well to bond the weld to the weldment better. Then, preheat with your torch, and weld in small sections to minimize the heat input. After each welded section, peen with your chipping hammer or air needle scaler. These techniques help prevent cracking of the casting.

Your other obstacle is the fluid that is all over it. Clean it as best you can before attempting the weld.

[thehat]

weld cast

Also you will want to V out the crack with a die grinder or small grinder and driil a small hole at each end of the crack to keep it from going any farther.Depend on yur welder you will want somewhere around 100-115 amps AC or DCEN. HTH

[Welder99]

Whitey82nd.
Another thing if you have tried using Ni55 or 99 with no luck.ide try to OLE stand by.....(BRAZING),..as mentioned (V)grove the area to be welded 60-90 degree included angle, and yes drill a hole at both ends of the crack.Pre-Heat then apply alot of Flux into the welded area.Oxy-Acetylene (OAW)process.Neutral flame.as you begin to heat the area to be Brazed look for the cast to become a low Orange in color.(Dont over heat)...then apply the the covered brazing rod into the bevel.moving the torch back n forth.(butter both sides of the bevel.Once done then begin to apply the brazing rod and torch in rythem.once you are done,cover the transmission with a heat blanket to slow the cooling.(this is the time you will see how well you have done),cast iron is very ridgid.No ductillity.as the cast begins to cool the pressures and stresses begin to move.the brass has some ductillity to it and absorbes alot of the stess.There are several types of cast.Grey being the most common.ive read alot about cast and have tried many types of process.BUT this has been the most sucessful to me.If you havent brazed alot...ide suggest an old cast iron exhaust manifold.Take a hammer and break it into pieces.them braze them back together...(if you can do that your ready to try the transmission).best of luck... welder99

[Paul Seaman]

Welder99- very accurate advise and good description you make it seem easy I've welded mounting ears back on a truck trans with Ni99 and for my bet that is where I would start.

Get ready my supplier here got me for about $20 per pound of rod so only buy what you have to they don't hold up very good unless you have a rod locker.

[Blondie_486]

Whitey,

Brazing is a very valid method of repairing cast iron. If the crack isn't in a place that will take a lot of stress such as the mounting ears I would personally opt to braze the crack especially if it's just causing a leak rather than a mounting issue.

I've sucessfully welded cast iron engine blocks that have had inadequate anti freeze protection and cracked between freeze plugs or up to them. A good bevel in the crack and a small 3/32 hole at each end of the crack. As Welder99 said don't get it too hot while brazing. I gradually heat the area surrounding the crack with the torch first and let the heat distribute a bit into the rest of the casting then proceed to the heating the crack to brazing temp.

If you don't have access to a heat blanket I'd cool it slowly by waving the torch over the work and gradually decreasing the frequency that you reheat and increasing the distance until it cools enough. This is especially important if you're working in an unheated garage in the middle of the winter in the midwest.

I've also had sucess welding cast with a 7018 electrode DC-, with a good preheat and post heat. The low hydrogen properties help to keep the weld and the adjacent cast from becoming brittle. We've repaired a couple of cast iron boilers this way when I worked at the boiler shop.

Blondie