Yukon Chromoly Rear Axle Kit, Dana 44, Jeep JK Non-Rubicon, 35 Spline, 32 Long. Yukon performance axles are built with high-tensile strength 4340 chromoly, use superior production methods that include cold roll formed splines, and feature advanced heat treating to create an axle of unmatched quality and durability.. Yukon high-performance axles are built with high-tensile strength 4340 chromoly, use superior production methods that include cold roll formed splines, and feature advanced induction coil heat treating to create an axle of unmatched quality and durability.