The Fiat 540 and 540DT tractors represent a robust line of utility vehicles produced from the 1970s into the 1980s, built upon Fiat Trattori's established heritage. These tractors, typically powered by naturally aspirated diesel engines from the Fiat 800 Series, offered reliable performance in the 45-60 HP range, making them suitable for a wide array of agricultural and utility tasks. Their design emphasizes mechanical simplicity and durability, featuring a manual constant mesh gearbox with typically eight forward and two reverse gears, a single-plate dry clutch, and mechanical or hydraulic braking systems. The 540 series is known for its straightforward operation and ease of maintenance, making it a dependable workhorse for demanding environments. This comprehensive workshop manual provides full service and repair instructions for the Fiat 540 and 540DT tractors. It covers all essential systems, including detailed procedures for engine diagnosis and overhaul, transmission and final drive repair, hydraulic system servicing, electrical system troubleshooting with wiring schematics, and maintenance of the braking, steering, cooling, fuel, front and rear axles, power take-off, and body/chassis components. The manual is designed to assist mechanics, independent service professionals, and knowledgeable owners in performing everything from routine maintenance and lubrication to complete overhauls and complex diagnostics, ensuring the longevity and optimal performance of the vehicle.