Abstract: A lubricating spline joint for providing a viscous damping function includes a first member defining an internal spline, a second member defining an external spline engaged therewith, a seal ring between the members at one end of the splines, and a radially inwardly facing chamber at the other end which is exposed to lubrication fluid. The improvement features an internal barrier for assuring a fixed internal radius R and thus a preselected centrifugal pressure head of the fluid mass in the chamber and about the splines, and a plurality of venting passages 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.