An installation includes at least a pressurized lubricating circuit for elements housed in the rocking crankcase, each circuit including a radial transfer bearing between two opposite cylindrical journals coaxial about the rocking axis, one fixed journal on a fixed part and one pivoting journal on a pivoting part integral with the pivoting crankcase. Each transfer bearing has two U-shaped annular gaskets facing each other and spaced apart along the rocking axis so as to define between them an annular pressurized liquid lubricant chamber. The annular chamber is supplied with pressurized liquid lubricant by at least a supply duct integrated in the fixed part and whose upstream part is connected to a pressurized lubricant source, and feeds the rocking crankcase with pressurized lubricant through a dispensing duct emerging into the rocking crankcase. The invention is useful for lubricating rocking power transmission boxes for convertible aircraft tilt rotors.