The Komatsu D20-6 and D21-6 series crawler dozers represent robust and reliable machinery designed for a variety of earthmoving applications. These machines are powered by the efficient 4D95S-W-1 engine, a 4-stroke diesel unit with a displacement of 3.3 liters, delivering approximately 60-65 horsepower. Engineered for durability and performance, the D20-6 and D21-6 models feature a water-cooled system and are equipped with either a hydrostatic transmission (HST) or a powershift transmission, offering variable speed control for precise operation. Their sturdy construction, with operating weights ranging from approximately 4,000 to 4,800 kg, and features like straight or PAT blades, ensure they are well-suited for demanding tasks in construction, agriculture, and land management. This workshop and service manual provides comprehensive guidance for the Komatsu D20-6/D21-6 crawler dozers and the associated 95 Series engine. Written in English, it covers essential maintenance procedures, detailed troubleshooting steps, and critical technical specifications necessary for optimal vehicle upkeep and repair. The manual is an indispensable resource for owners, mechanics, and technicians, offering the in-depth information required to maintain the integrity, performance, and longevity of these powerful machines. It details capacities for engine oil, coolant, and hydraulic oil, alongside operational specifications such as ground pressure, track gauge, and ground clearance, ensuring all aspects of the vehicle's service and operation are thoroughly addressed.