Back to material science:

Cab, I don't know of any cast steel driveline parts. Maybe you do. I do know that nodular cast iron, compacted graphite iron, regular steel and cast steel have the same stiffness/spring rate/modulus of elasticity, and that is around 30 million units, while gray iron which is all the other stuff used in automotive applications, has about 20 million, and aluminum has about 13million.

That means that a stock housing made out of nodular iron is 50% stiffer than a stock gray iron case. That's with everything being dimensionally the same. If Cass's housing is heavier, with thicker sections and billet caps, it could easily be 100% or more stiffer than the gray iron case. In other words, more than twice as stiff.

We should be able to agree that the reasons rear ends break in the majority of cases is the gears moving away from each other, which increases the moment on the root of the tooth. Doesn't matter if it's the case flexing from the pinion or the axle tubes or both, a stiffer case will be able to withstand more force or torque. So, these housings are an improvement over stock and more power can be put on the ground.

The aluminum case was designed to be stronger than the stock case and I believe it used heavier sections to be stiffer, had to be that way because the aluminum is more flexible. And I'm sure (even though some ignoramus poked fun at this statement earlier) that modern design methods were used to design this case. Too bad it's no longer available but as I couldn't afford one then I can't afford one now either.

R.

PS: Cast steel may have a greater tensile strength than nodular or CG iron, but most rear ends don't fail because the case breaks. As cast steel, cast iron and CG iron have the same modulus of elasticity so they will react the same way to a load.