This document provides comprehensive factory service and repair information for the John Deere 120 Hydrostatic Tractor. John Deere is a reputable manufacturer known for its durable agricultural and construction equipment. The 120 Hydrostatic Tractor series is recognized for its utility and advanced hydrostatic drive systems, designed for reliable performance in demanding environments. This manual details the engineering and operational aspects of the tractor, offering in-depth guidance for maintenance and repair. The purpose of this manual is to serve as an authoritative resource for technicians, mechanics, and owners. It covers a wide array of topics, including general maintenance, periodic lubrication, service charts, and specific repair procedures for all major systems such as the engine, hydrostatic transmission, powertrain, chassis, and electrical systems. Detailed troubleshooting guides, wiring diagrams, safety instructions, and specifications for fluids and lubricants are also included, ensuring that users have the necessary knowledge to maintain the optimal performance and longevity of their John Deere 120 Hydrostatic Tractor.