Abstract: A spline joint comprising: a sidewall extending along and around an axis defining an axial direction of the joint, wherein the sidewall defines a passage extending from a first end to a second end; wherein the passage is arranged to receive an end of a shaft at the first end; and wherein an engagement portion of an inner surface of the sidewall adjacent the first end is arranged to engage a shaft received in the passage, to transmit torque to the shaft; a base wall extending across the passage and axially spaced from the first end of the passage; an opening formed through the base wall; and an inner wall extending around the opening and in the axial direction from the base wall, such that an annular trough arranged to retain lubricant for the spline joint is defined between the sidewall and the inner wall.