Welding cast iron transmission housing

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dlundblad

dlundblad

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Tractor related once again,

I have a early 90's Kubota garden tractor with a cracked transmission housing. According to the PO and original owner, he let a neighbor borrow the tractor years ago. Rather than using ramps for either loading or unloading, they grabbed it by the body behind the seat. The body is fiberglass and the tractor is built like a tank so the body cracked and the tractor was dropped.. hence the cracked transmission.

It was welded, but the weld is no longer holding and it's leaking again. The replacement part is $450 assuming that's all that needs replaced. I know nothing about hydrostatic transmissions so will probably have the dealer do the work. Another alternative would be having a professional re weld it, but my concern is the weld only holding for so long and it failing again. I can have the transmission off in about an hour.

Thoughts?
 
There are special welding rods for cast iron. Check out YouTube, there are a few people trying them out.
 
Originally Posted by skyactiv
Depending on the severity, JB Weld might do the trick.

+1
If all you have to do is stop it from leaking, JB Weld should do the trick.
 
Actually, $450 doesn't sound bad for a replacement transmission. The hassle and expense of doing a marginal weld repair on a cast iron housing sounds worse to me. To be done correctly, the transmission would have to be completely disassembled and the housing cleaned, then preheated and welded with high-Nickel rod. That whole process sounds more expensive than installing a new transmission. Or maybe you can find a good used or remanned one from a Kubota dealer
 
Originally Posted by A_Harman
Actually, $450 doesn't sound bad for a replacement transmission. The hassle and expense of doing a marginal weld repair on a cast iron housing sounds worse to me. To be done correctly, the transmission would have to be completely disassembled and the housing cleaned, then preheated and welded with high-Nickel rod. That whole process sounds more expensive than installing a new transmission. Or maybe you can find a good used or remanned one from a Kubota dealer


This is just 1 of 3 pieces that make the housing. A replacement transmission is 2.2k.
 
I'd have to agree with the JB Weld suggestion. I had a buddy that cracked a cast iron engine block. It was down by the oil pan. He used JB Weld and it worked for over 100k miles till he sold the car.
 
If you have the model of transmission, maybe a used one will pop up on eBay . There are 2-3 big places that do small engines , mowers and tractors around the Annapolis / Baltimore area, and they might be able to source a good used trans.
 
If you could do a good weld AND reinforce the weld with a tension type strap would probable solve your problem for life. Somehow use a turnbuckle tension strap to reinforce the weld. ED
 
Originally Posted by 2009Edge
Grind a V and use Oxy Acetylene and brass .
I used this method on cast iron exhaust manifolds and had good results.


That sounds like the best idea to me.
 
Should be fairly easy for a competent welder. I've welded a lot of cast successfully and I am not even good.

Weld prep is crucial, grind out the old stuff, don't grind more than about 1/3 of the way through the casting if you can avoid it. And make sure it's clean. Denatured alcohol on a rag works well.

No matter what DO NOT use carburetor cleaner, choke cleaner, brake cleaner, or aerosol parts cleaner from the auto store to clean this weld prep. Some of those chemicals turn into a poison at welding heat that can be fatal in very low concentrations.

There is a stick welding (SMAW) rod available with a high nickel content, it's soft enough to accommodate the mechanical properties / expansion and contraction of cast iron heating and cooling. Alternately, if you know anyone who can weld TIG (aka GTAW) they could use a silicon bronze rod, also plenty strong enough.

As other posters have observed, Oxy-Acetylene brazing is an option, but that would be my last choice if the transmission were still assembled because of the heat.

If you are going to disassemble the transmission subsequent to removal it will be easier all the way around to weld but not by any means essential. A mild pre-heat and wrapping the unit in a heat proof blanket and letting it cool slowly will help with the durability and quality of the repair.
 
First photo is the top view where it cracked at the upper left mount. Middle photo just shows the 4 bolt holes. (Even though the 2 upper bolts are hidden.) Bottom photo is where the crack went diagonal to the bottom right mount.

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65F71374-FA1C-4B4F-AE7A-9CA0FD2F2F75.webp


D07BFA41-BB16-42CA-BA25-97BF4FD4C067.webp
 
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I used to bring cracked cast iron diesel parts to a guy years ago that was AWESOME at welding cast iron. He used to heat the parts in ovens he would build around the castings until they were glowing and then he would weld them.
Whatever he did was the right way to do it because none of the stuff he did ever opened up again. After he retired, no one picked up his business so that was the end of that.

The other place in the area that did the same kind of work was awful. I never got a successful repair from them and gave up trying.
 
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