1. There are three types of Rockwell axleshafts: Bendix, Rezepa, and Spicer (shown). Our sources indicated that the Spicer (U-joint) style is the strongest, as it's the only one of the three made from heat-treated steel. The other two are comprised of cast metals. With the substantial 16-spline shaft measuring in an outside diameter of 1.62 inches, it's going to take a good bit of hammering before these shafts go pop.