A gas turbine engine having a coupling element for coupling a first shaft to a second shaft, the second shaft being substantially axially aligned with the first shaft, the coupling element provided with an exterior surface that engages an opposing interior surface of the first shaft and an interior surface that engages an opposing exterior surface of the second shaft to facilitate torque transfer between the first shaft and the second shaft when rotated together, wherein the coupling element and at least one of the first and second shafts cooperate to define at least one fluid passageway therebetween.