Abstract: A system is provided for a product pump drive for pumping fluids or substances into or out of a tanker-trailer towed by a tractor, the system including an auxiliary diesel engine mounted on the tractor, the engine operating a hydraulic pump used to operate a hydraulic motor operatively coupled to a product pump. The system can further include a high-pressure shutdown mechanism to shut down the engine if the pressure of the hydraulic fluid pumped by the hydraulic pump exceeds a high-pressure threshold. The system can also include an air conditioning unit and/or an electrical generator operatively coupled to the auxiliary diesel engine.