3.09 4 Speed Gear Set Strength

That ain't quite true. Some gearsets are stronger than others, same in a rear axle. Generally, lower gear ring / pinions are weaker than higher geared ring/ pinions. "I've always been told" the 3:1 low is weaker. It makes sense because the driver gear on the cluster is smaller


The weakest gear on ANY 833 is 3rd. So it’s true. The 3.09 box is no weaker than any other 833.

As far as gear materiel, any production gear box has the same gear materiel.