A grease fitting replacement tool Includes a housing, a shaft, an adaptive socket, a loosening device, loosening device includes a packed coupling, a stem housing, and a stem drive system, the stem drive system includes a stem, a threaded mount, and an actuator, a main valve, a fall-out trap, a pressure port valve, a vent valve, a pressure gauge, and a temporary mounting system. A method of using a grease fitting replacement tool to replace a grease fitting of a piece of equipment while the piece of equipment remains in operation.