Welding transmission case

fiatfan · Dec 29, 2018

I could use some advise from someone who has, with success, welded some damage on an outer transmission case. I´d like to know what material was used, and the method, that is if you need to heat the case before welding f.ex. So that I know what I´m talking about when I´m looking for someone who can help me with the welding. I´ve got this crazy idea to "customise" the outer casing.....don´t know if it´s doable, but it looks good in my head. Also looking for a damaged outer case btw....

olympus · Dec 30, 2018

My inner chain case was heavily grooved & cracked where the poorly shined case was machined away by the drive chain... I took it to one of my repair agents and standard MIG welding wire And kit was used th build the cover back up before being machined back down.

lcrken · Dec 30, 2018

I've TIG/GTAW welded them with 4043 rod with no problems. I didn't pre-heat, but it couldn't hurt to do so. I've been reading recently about a newer alloy, 4943 being an improvement on 4043, but I haven't tried it yet. Supposed to be stronger and wet out better.

Ken

eskasteve · Dec 30, 2018

Outer gearbox case is $175 new from Old Britts. In my mind, better than welding and machining. Probably less expensive, too.

rotorwrinch · Dec 30, 2018

Had a local welding wizard try the Hobart 4943 rod in doing some test welding on a used Commando cylinder head. In the past the welding of that sort always utilized the tried and generally true 4043 rod. Unfortunately cast cylinder heads loose more of their heat treat toughness the more they are welded on. I was trying to better the results when saving or modifying a cylinder head. It was realized after much conversation and consult from a highly regarded heat treating expert in my area, that the a used Norton cylinder head was likely the among the worst candidates to be annealed and re-heat treated. The 4943 rod was heat treatable and the 4043 does not respond favorably to standard heat treatment. What does this have to do with fiatfan's original post ? Well, my preliminary observations and the work of my welder indicates that 4943 rod is likely a better choice of welding rod . I would recommend finding a sacrificial gearbox for testing purposes prior to getting committed on the gearbox you intend to use. I would also recommend focusing on the idea of air or water quenching to expedite aging and allow as much time allowing for the toughness to age back into the casting. There are several gearbox shells stashed around here that were welded up to support the layshaft bearing. Those boxes were bulked up with 4043 and none have made it to the sacrificed to the gods of speed collection. The 4943 rod should give even better results.

dantriumph · Dec 31, 2018

Hi.
I haven´t welded a gearbox cover, but have just repaired a fork slider for a friend. I pre heat to +/- 200 degree C, weld with AlSi wire and cool down slowly. For cooling down I use a box full of Rockwool (Isolation).

I´m a Tig welder, but my experience with cast alu is limited. Anyway, this has worked for me.
Dan

fiatfan · Dec 31, 2018

rotorwrinch said:
Had a local welding wizard try the Hobart 4943 rod in doing some test welding on a used Commando cylinder head. In the past the welding of that sort always utilized the tried and generally true 4043 rod. Unfortunately cast cylinder heads loose more of their heat treat toughness the more they are welded on. I was trying to better the results when saving or modifying a cylinder head. It was realized after much conversation and consult from a highly regarded heat treating expert in my area, that the a used Norton cylinder head was likely the among the worst candidates to be annealed and re-heat treated. The 4943 rod was heat treatable and the 4043 does not respond favorably to standard heat treatment. What does this have to do with fiatfan's original post ? Well, my preliminary observations and the work of my welder indicates that 4943 rod is likely a better choice of welding rod . I would recommend finding a sacrificial gearbox for testing purposes prior to getting committed on the gearbox you intend to use. I would also recommend focusing on the idea of air or water quenching to expedite aging and allow as much time allowing for the toughness to age back into the casting. There are several gearbox shells stashed around here that were welded up to support the layshaft bearing. Those boxes were bulked up with 4043 and none have made it to the sacrificed to the gods of speed collection. The 4943 rod should give even better results.

Thanks for the input all is interresting to me now. But it´s the outer primary transmission casing, not a gearbox I was asking about. Maybe I wasn´t clear on that.

fiatfan · Dec 31, 2018

Thanks for the replies, I was obviously a bit unclear. It´s the outer primary casing I´m wondering about. It´s not easy sometimes when there´s two different kinds of English....And I don´t have any of them as my native language.... But I think the advise about what rods to use and so on is valid anyway so thanks.

fiatfan · Dec 31, 2018

eskasteve said:
Outer gearbox case is $175 new from Old Britts. In my mind, better than welding and machining. Probably less expensive, too.

As I just wrote I didn´t get it right in the OP, it´s the outer primary casing I´m asking about. And I´m looking for one that´s been a bit damaged, for customising work.

lcrken · Dec 31, 2018

The observations here about TIG welding with 4043 or 4943 should also be applicable to the outer primary cover. I haven't welded on one, but back in the late '70s I had one trimmed for ground clearance at the bottom of the alternator bubble, with a flat plate welded on by a local welding shop (back before I had a TIG setup). He used TIG and most likely 4043 rod, and it came out great. I don't know if he used any pre-heat.

Ken

kommando · Dec 31, 2018

I had an outer primary case welded and it bubbled up and the more it was welded the bubbling just moved to the outer edge of the welded section, the same welder has been welding all different Brit cases for me for years and never had an issue. The Norton crankcases he did for me at the same time were fine. Not sure what the issue was, he played around with the settings but with no change in the bubbles, maybe the alloy had a contaminant in that casing. I have dressed it flat and polished it as it is solid but on the surface there is a line of these bubbles around the welded alloy.

Stephen Hill · Dec 31, 2018

I had a couple of primary covers welded, but was never all that happy with the results. The covers warped and needed a lots of filing to get them somewhat back into shape. The sealing surfaces also warped, and there is not much you can do with that. The filler rod would show up as a different colour when you polished it or would corrode to a different colour when it got wet.

For very small cracks and dents, hammer and dolly the surfaces level, then use epoxy on the inside.

Kind of depends on how fussy you are, and how much $ you want to throw at the problem. I usually end up replacing the cover.

Stephen Hill

Danno · Jan 1, 2019

I broke the drain plug boss on the SS Clone's outer primary and had it welded by a local expert, who thickened the boss to make it stronger. I ground, filed and polished it to shape and then drilled and tapped a new drain hole. Without a stock cover to compare it to, you'd never know. Of course, the drain plug is quite a ways from the gasket surface.

Welding transmission case

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