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
Grant