A hydraulic mantle system for a gyratory rock crusher enables the safe, quick and efficient replacement of a worn or deformed mantle. The system includes a main shaft, an annular nut, an annular hydraulic piston and an annular mantle. The main shaft has a flange and external threads adjacent the flange. The annular nut body has side surfaces and internal threads that are threaded onto the external threads of the main shaft. The annular hydraulic piston has side surfaces that slidingly engage the side surfaces of the annular nut body. The annular mantle has an upper neck portion and a lower edge portion. The main shaft extends through the upper neck portion. The upper neck portion of the annular mantle is compressed between the flange of the main shaft and the annular hydraulic piston.