A shaft assembly having: a first shaft with an inner facing surface having: an inner facing spline extending between spline ends; an inner facing projection, adjacent to one of the spline ends, extending to an inner facing projection surface; and an inner facing projection seat, adjacent to another of the spline ends; and a second shaft having an outer facing surface having: an outer facing spline extending between spline ends; an outer facing projection, adjacent to one of the spline ends of the outer facing spline, extending to an outer projection surface; and an outer facing projection seat, adjacent to another of the ends of the outer facing spline; the first shaft at least partially surrounds the second shaft; the inner facing projection surface is disposed against the outer facing projection seat; and the outer facing projection surface disposed against the inner facing projection seat.