The International Harvester 1086 is a robust agricultural tractor, produced between 1976 and 1981, renowned for its powerful DT-466 diesel engine and the versatile T-144 Power Transfer transmission offering 16 forward gears. This model, a significant part of the successful Hydro 70/86 series, was manufactured primarily in Rockford, Illinois, and is recognized for its strong engineering and reliable performance in heavy draft work. Its design prioritized operator efficiency and durability, making it a staple in the agricultural industry and earning it industry recognition for setting benchmarks in its era. This comprehensive workshop service repair manual provides in-depth coverage for the International Harvester 1086. It details general information, specifications, and step-by-step repair procedures for all major systems, including the engine, cooling system, fuel system, powertrain, clutch, differential lock, electrical system, brakes, and hydraulic system. With hundreds of photos and illustrations, this manual is an essential resource for do-it-yourself owners and experienced mechanics alike, offering troubleshooting guidance, particularly for electrical systems, and ensuring optimal maintenance and repair for the tractor.