This factory service repair manual covers the International Harvester 1206, 1256, and 1456 tractors, produced between approximately 1963 and 1969. These robust machines, powered by International Harvester DT-402 and DT-429 diesel engines, represented a significant advancement in agricultural power and technology during their era. Known for their reliability and strong performance, these tractors were designed to be dependable workhorses for farm owners and operators. The manual provides comprehensive information to ensure these iconic tractors continue to operate at their peak efficiency. This comprehensive manual offers factory-level repair and maintenance guidance for farm owners, mechanics, and restoration specialists. It details engine service, transmission repair, hydraulic system maintenance, and electrical system troubleshooting, among other critical components. With hundreds of pages of information, including detailed overhaul procedures, diagnostic guides, adjustment specifications, and technical data such as torque values and clearances, this manual is an indispensable resource. It empowers users to perform all necessary maintenance and repairs, ensuring the longevity and optimal performance of their International Harvester tractors.