This Technical Service Manual provides comprehensive information for the John Deere Series 220 Diesel Engines, generation CTM3. These robust diesel engines are engineered for reliability and performance, serving as dependable power units across various applications. The manual covers multiple engine variants, including the 3TN66, 3TNA72, 3TN75, 3TN78, 3TNC78, 3TN82, 3TNA82, 3TN84, 4TN78T, 4TN82, 4TN84(T), and 4TN100 models, ensuring broad coverage for owners and technicians. The purpose of this manual is to equip users with the knowledge necessary for effective maintenance, repair, and diagnosis of the John Deere Series 220 Diesel Engines. It details essential procedures for the air intake, fuel system, and electrical system, along with preventative maintenance schedules and service interval guidance. With clear, step-by-step instructions and detailed illustrations, this manual serves as an indispensable resource for maintaining the optimal performance and longevity of your John Deere diesel engine.