A lubricated spline joint (30) for providing a viscous damping function includes a first member (32) defining an internal spline (62), a second member (34) defining an external spline (64) engaged therewith, a seal ring (76) between the members (32, 34) at one end of the splines, and a radially inwardly facing chamber (80) at the other end which is exposed to lubrication fluid. The improvement features an internal barrier (84) for assuring a fixed internal radius R and thus a preselected centrifugal pressure head of the fluid mass (86) in the chamber (80) and about the splines, and a plurality of venting passages (94) located radially outwardly of the radius R for continually exhausting fluid from the splines as a result of centrifugal force so that fresh and/or less aerated fluid is circulated through the splines.