A gas turbine engine and method of assembling the same

A coupling shaft assembly (62) for a gas turbine engine (20) includes a forward coupling shaft section (64) with a forward interface spline (68) and a forward mid shaft interface spline (68) and an aft coupling shaft section (66) includes an aft mid shaft interface spline (72) and an aft interface spline (74). The aft mid shaft interface spline (72) is engageable with the forward mid shaft interface spline (70).