This service manual covers the Nuffield Universal Three and Four tractors, encompassing various engine types including OEC Three Cylinder Diesel, OEA Four Cylinder Diesel, and ETC, ETD Petrol & V.O. models. It details essential systems such as ignition, cooling, fuel, clutch, gearbox, transmission, steering, axles, wheels, tires, braking, electrical, drawbar, and lubrication. The manual also addresses optional equipment and implement settings, providing comprehensive information for these robust agricultural machines. The purpose of this manual is to serve as a complete factory service and repair guide for owners and technicians. It offers step-by-step instructions, detailed illustrations, diagrams, and specifications to facilitate maintenance, repair, and troubleshooting. By applying the knowledge contained within, users can effectively diagnose issues, perform necessary repairs, and ensure the optimal performance and longevity of their Nuffield Universal Three and Four tractors.