This English-language Shop Manual provides comprehensive technical information for Komatsu Internal Combustion Engines, specifically the 3D72-2, 3D75-2, 3D78-1, 3D84-2, 3D83N-2, and 4D84-2 diesel engine lineup. These engines are designed for robust performance in demanding industrial and agricultural equipment applications. The manual details the engineering and reliability inherent in these diesel powerplants, which are also cross-referenced to their Yanmar counterparts for enhanced serviceability. This manual serves as an essential resource for maintaining and repairing the specified Komatsu engines. It covers a wide range of critical topics, including detailed maintenance procedures, diagnostic troubleshooting guides, essential technical specifications, and important safety guidelines. By following the instructions and information contained within these 262 pages, owners, mechanics, and technicians can ensure the optimal performance, longevity, and safe operation of their equipment.