The invention relates to a system and process for removing hardened lubricant, contaminants and other debris from an enclosed gearbox of an actuator in the gas, oil, and power industries that allows the oil or gas pipeline to continue to operate uninterrupted during servicing. The system operates at a low pressure and includes two pumps: an upstream pump that pumps a non-corrosive mineral oil-based cleaning agent into the gearbox; and a downstream pump that pulls off the pressure from within the gearbox as part of the circulation of the flush system. The system and process are further provided with a clean tank for storing an influent cleaning agent, a waste tank for storing an effluent cleaning agent, and a circulation tank used during the flush circulation process. The system and process may also include a rotatable mounting assembly that is secured to the gearbox of the actuator.