A rotation rod assembly comprising: a first linkage rod having a first annular body portion fixedly secured to and extending axially therefrom, the first annular body portion having an inner surface defining a first bore axially extending partially into the first annular body portion , the first annular body portion having a first axial end and second axial end, the first axial end being closed and the second axial end having an opening with a plug adjustably secured therein, the plug having a second bore extending therethrough, the first linkage rod being fixedly secured to a frame; a second linkage rod having a piston section extending axially therefrom, the piston section being coaxial with the first linkage rod and the plug , the piston section being disposed for rotation in the first bore , the inner surface surrounding the piston section , the second linkage rod extending through the second bore and rotatable relative to the plug , the piston section being axially restrained by the first end and the plug ; the piston section having a first bushing and a second bushing secured to at least one outer surface of the piston section , the first bushing and the second bushing having a lubrication groove formed in an axially and a radially outer surface thereof, at least one of the first bushing and the second bushing being in sliding engagement with portions of the inner surface , the first end and a portion of the plug ; a barrier for preventing flow of the grease inside the piston section ; and a flow path for conveying grease around the piston section , the flow path (F) comprising a first radial circuit in the first bushing , a first axial circuit in the first bushing , a second axial circuit around a radial outer surface of the piston section, a third axial circuit in the second bushing , and a second radial circuit in the second bushing . a first linkage rod having a first annular body portion fixedly secured to and extending axially therefrom, the first annular body portion having an inner surface defining a first bore axially extending partially into the first annular body portion , the first annular body portion having a first axial end and second axial end, the first axial end being closed and the second axial end having an opening with a plug adjustably secured therein, the plug having a second bore extending therethrough, the first linkage rod being fixedly secured to a frame; a second linkage rod having a piston section extending axially therefrom, the piston section being coaxial with the first linkage rod and the plug , the piston section being disposed for rotation in the first bore , the inner surface surrounding the piston section , the second linkage rod extending through the second bore and rotatable relative to the plug , the piston section being axially restrained by the first end and the plug ; the piston section having a first bushing and a second bushing secured to at least one outer surface of the piston section , the first bushing and the second bushing having a lubrication groove formed in an axially and a radially outer surface thereof, at least one of the first bushing and the second bushing being in sliding engagement with portions of the inner surface , the first end and a portion of the plug ; a barrier for preventing flow of the grease inside the piston section ; and a flow path for conveying grease around the piston section , the flow path (F) comprising a first radial circuit in the first bushing , a first axial circuit in the first bushing , a second axial circuit around a radial outer surface of the piston section, a third axial circuit in the second bushing , and a second radial circuit in the second bushing . <EOS>