406 = DANA/SPICER DIFFERENTIAL

This is an internal gear kit for Dana S-44 axles. The Dana 44 axle has seen various configurations over its production run (1953-1993), including changes in axle shaft spline count (from 19 to 30 spline between 1966 and 1970) and differential side bearing inner race diameter (mid-1960s). There are also different ring gear flange offsets for "Fast" (2.72-3.73 gear sets) and "Slow" (3.92-5.89 ratios) differential cases, typically 30 spline assemblies. It is crucial to verify existing components before ordering, as older axles may have non-stock parts or swapped assemblies. Ring gear bolts (Dana 44 uses QU40209, quantity 10) are torque-to-yield fasteners and should not be reused.