Cracked housing repair

[Derek]

When cleaning a final housing this evening, I noticed a small crack starting through a bolt hole. I was thinking of opening it up and brazing it. Since its still a short crack shouldn't be a problem grinding it all the way out to keep it from running. Its a 40c. Any thing to watch out for brazing on these older housings? Is this a common issue on 40c final drives? This housing is in really good shape besides this issue.



Derek

[original possum]

I wouldn't trust brass to have enough strength for such a crack. Have it ground and welded professionally with so much at stake.

[Hurlbutt]

One step you might consider in the repair process would be to drill a stop hole at the end of the crack. The crack creates a stress concentration and the drilling operation will relieve the stress.
Concerning brazing vs welding; with either operation heat soak it well. Heating will also relieve stress and also reduces stresses caused by the repair process. Some years back I had the privilege of repairing the casting of a JD No 9 sickle bar mower after one of the pivot pins for the bar was lost while mowing. The casting broke at the other pivot pin. After relief grinding and soaking it in the wood hearer for a couple hours I spent a good amount of time with the oxy-acetylene torch with flux coated brazing rod. That is a high load application and the repair never failed. What ever method of repair you use be sure to heat soak to minimize stress cause by the repair process.

[gus]

I had a crack repaired and they even added a missing ear on the housing. They used heat and special rod. Cost less than $100 at the time. It's been 10 years and still holding! Worth checking on a pro to do it.

[hydrogeo]

I think these housings are cast steel, not cast iron. Cast steel is easy to weld, although a little pre-heat would be good. Cast iron is quite a bit trickier, you'd need to preheat the entire casting evenly and weld it stick with some nickel rod. In either case brazing is also an option too. Unlike what others have said I wouldn't worry about a properly done braze joint not being strong enough. I also agree that if you can drill stop holes that would be a good idea.

[Lavoy]

They are cast iron, vee it out, braze it and run it. There is no concentrated stress on the hole, it is distributed around the hole by the bearing quill. It is likely a crack from prior in it's life when a bearing went out and played nutcracker with the gears, and cracked the case. Normally it just blows that top section of the final drive case off, but they got lucky on this one. I have had multiple cases over the years that have been welded 20 more than this one will need, and ran for years. It isn't the quill that causes the cracks or breaks, it is the pinion gear hitting the top of the case and concentrating the force on a smaller area.
Lavoy

[sonny]

I have brazed castings of all kinds! Piece of cake to do! Pre-heating works best then go from there, cool slowly if possible helps too.

[Derek]

Thanks for all the replies. Good to know brazing will work fine with this cast. I've done enough cast repairs in the past to know not all cast iron is equal and was not sure about the quality of iron Deere used for these. This is not an area for welding, even with NI99 rod it would be tough to re-drill and tap the hole not to mention the the sharp points on the tap could create stress risers in the weld material and could possibly crack down the road. I was thinking the quill would distribute the load equally around the bore, thanks for confirming that Lavoy. I'll tig braze it and post pics when its done.