welding axle tubes ?

tom h

Active Member
i've read anecdotal reports that axle tubes are simply pressed-in.

and, have "heard of" axle tubes sometimes rotating or getting twisted at the center housing.

Is there any benefit to having the axle tubes tack-welded or full welded, on a predominantly (but not exclusively) street car? or is it a waste of effort?

The stock axle tubes are pressed in to the center housing. They are also welded to the center thru holes that are cast into the center section. If the factory did a good job, you shouldn't have a problem. If the factory did a bad job, I've seen problems arise on a grandma car. If you want extra insurance against any problems, you can weld the tubes to the center. If you're going to weld them, use a stick welder, get the correct rod, and heat the entire area on the housing before welding to eliminate to possibility for any distortion. To do it correctly, I would recommend disassembing the rear prior to heating/welding.
the rotational stress of a launch is imposed on the center carrier only, but the axle tubes are pulled forward linierly towards the front of the vehicle as the tires pull car down the track, ( because the tires in the rear we think that the car is pushed, but if you look at it from the center off the rear end, it is pulling the housing ends forward) the tubes are only put in rotational stress during breaking, with that being said, the axles on the 8.5 gm area pressed in and welded with rosete style welds threw the housing, being that the housing is made of cast iron, and welding by arc means is not the best manner, and the 2 metals when fused make a real weak joint, but if you look a the design of the welds, the are not true welds, but more of a means of pinning the pressed ends in, and keeping them from rotating in the houseing the stress is taken by the press fit mainly, you will not gain much by welding the end joint of the housing, and might take away some of the press fit by heating the ends up with the welding, the only proper way to weld cast iron is by brazing, arc welding is seldom recomended,and in industry brazing is almost always used, even on heavy machinery, hoep that helps, so in the end, that is why it is not recomended to weld the ends, but a back brace that works with the girdled caps, that has the tubes that connect the ends of the housing to the center housing, preloading the rearend to prevent that pulling of the tubes forward that i talked about later. hope it helped
It is correct that no one would recommend welding cast iron to steel. However, in this case sometimes there is no choice. They do make special welding rods for this purpose. It can't be done with a mig or tig welder. Also, welding supply stores sell special crayons to mark the housing with that change color when the housing is preheated to the correct temperature prior to welding. This temperature is somewhat important. If the housing is over heated, like n20junkie said, the integrity of the press-fit may be compromised. If the housing is under heated, the weld WILL crack as it cools and it could also distort the housing as a result of centralized thermal expansion/contraction. The rear must be heated very evenly around the tube and housing prior to welding. It is also recommended to tap on the weld with a hammer as it cools to further reduce the stress on the weld as it contracts during cooling. I have done two nine sec cars, and many ten sec cars with zero failures and zero distortion resulting from any welding. I welded the center housing to the axle tubes on my ten sec Nova, and have had no problems running three years now. Bottom line- if the guy welding follows the correct procedure, it would be unlikely to have any problems. Then again, if your are not running a combo with both good traction and a fair amount of horsepower, I would not recommend this procedure. As far as the flexing issue goes, I have never seen a problem resulting from it. There is a good amount of stress exerted on the weld, but IMO I dont see how flexing would be an issue with a weld that runs the circumferance of an axle tube. If you're still concerned about linear stress, a back brace will eliminate any linier flexing as was mentioned earlier. As for major rear end suppliers, they aren't gonna make any money by telling you to fix what you got instead of buying new from them, and those 9 inch ford rears suck up big power and are really heavy (the good part is that it will be completely indestructable). This has been my experience over many years of shortening/fitting/ and building rears for special applications, so take it for what it's worth and most of all have fun!

Originally posted by snodgrass
... Then again, if your are not running a combo with both good traction and a fair amount of horsepower, I would not recommend this procedure... -Jeff
That's definitely me! Since this is a lot more complex than meets the eye, and since my car is low mileage and not abused , this sis something I'll avoid for my car. Thx guys.
I had mine done by a chassis shop who has won three national NHRA events and build tube style cars all the way up to pro mods. If you are running ladder bars or a four link and some steam rollers you crazy to think that when the drive shaft starts to lift the pinion at launch and the tubes arent going anywhere are they going to hold,not a chance. I know there will be alot of I dont have any problem replies but if your running wide tire over 12-14" and have a working suspension you might or will have trouble. Another good piece of advice from him was to check axle flange run out to see if the tubes moved during welding. Cheap insurance in my book by the way Im running a 12 bolt but would be the same for a 8.5.
i will agree that the rear end can be welded, if it was on my car i would pefer a tig welded rear, but stick welding is still the methode of choice for industry and the array of welding rods is unbelieveable, and as stated, there are specific rods for iron/steel welding, i would say that only an experianced welder in stick techniques should attempt such a weld, one thing that i forgot was that a toque is applied to the tubes due to the lower mounts, but the bulk of the torque is applied to the upper mounts, which are on the housing, side note, this is one of the more intellegent discussions i have seen on here in a while.
309 stainless is going to be the rod

Of choice for welding the cast center housing to the steel axle tubes. 309 has properties of both the cast and the steel which makes it an ideal rod for this app {doesn't matter if your stick,mig or tig welding} My choice will always be tig. :D
i will second the use of stainless rod, for those that are not welding savy, stainless is classified as a low carbon steel, and is used in areas where the introduction of carbon will cause hardening of the metal to the point of it becomming brittle, and stainless is also softer due to the lack of carbon, and will flex more without cracking similar to the iron in the center housing, not may people will load a roll of wire in a mig welder unless they have alot of work to do with that material, stick welding is always an alternative but unless an experianced person is doing the taks the work will usually be overheated, tig always the most percision, and the heat can be applied with percision, if you are going to do this, finding someone to do it will probably involve looking other than chassis shops, as most chassis shops do not have much experiance with materials other than high carbon steels used in chassis construction, and if they are knowlabeable in low carbon steels, it is almost never in a disimilar metal fabrication, an industrial weld shop will be abe to do it as these are certified welders unlike most chassis chops, just do your homework,
weld tubes

I/ve welded 4 with my trusty Miller 250 wire welder. All 4 are still going strong. Glad I didn/t have this post to read before welding. I firmly believe if you wire wheel the area CLEAN, you can put 3 --3/4 in. spot welds that will hold without a problem. I can see where welding all the way around could cause a problem.
in my race car i had bought the currie 9+ center housing as a base for my 4 link rear, and all i can say about the product is great, i would recomed those rear ends and certer housings as a starting basis for any project, little off topic, but in case you guys wanted to know