An assembly to restrict fluid flow through the bearing section of a positive displacement or progressive cavity pump or motor. The assembly fits within the bearing chamber and includes an upper ring member, a lower ring member, an outer ring member and a floating member. The floating ring member is axially disposed between the upper and lower ring members. The floating ring member is also disposed at least partially around a drive shaft and is radially movable and constrained inwardly of the outer ring member. The floating ring member has a radial clearance between the drive shaft and a floating ring member inner surface with the radial clearance varying depending on the relative position of the floating ring member to the outer ring member.