This comprehensive John Deere 6620, Sidehill 6620, 7720 & 8820 Combines Service Technical Manual (TM1202) provides detailed repair and maintenance instructions for these models. It is an invaluable resource for both experienced mechanics and DIY enthusiasts who wish to understand and service their machines thoroughly.

This manual covers a wide range of topics, including:

* **General Specifications and Diagnostics:** Learn about the machine's specifications, understand diagnostic procedures, and troubleshoot common issues.
* **Engine Repair:** Dive deep into engine repair, covering components such as the cylinder head, valves, camshaft, block, liners, pistons, rods, crankshaft, main bearings, lubrication system, and cooling system.
* **Fuel and Air System Repair:** Explore the air intake system, diesel fuel system, and control linkage for optimal performance.
* **Electrical Repair:** This section covers harness replacement, electrical system diagnosis, charging circuit repair, starting circuit repair, lights, instruments, and accessories.
* **Power Train Repair:** Gain insights into the clutch, transmission, differential, final drive, hydrostatic drive systems (Sundstrand and Eaton), 4-wheel drive systems (planetary gearing and cam lobe), Posi-Torq ground drive, and tires and wheels.
* **Steering and Brakes Repair:** Understand the power steering and brake systems, including their repair and maintenance.
* **Hydraulic Repair:** This section covers the hydraulic reservoir, pump, valves, cylinders, motors, and accumulator.
* **Separator Shell Repair:** Explore the rear hood, cylinder rear cover, and separator uprights.
* **Operator Station Repair:** Focus on the air conditioning, air intake (pressurizer), heating, personal posture seat, and other miscellaneous components.
* **Header Repair:** Learn about the repair and maintenance of various headers, including the 200 and 900 series cutting platforms, 40 series corn heads, and 50, 50A series row-crop heads.
* **Feeder House Repair:** This section covers the feeder conveyor chain, drum, drives, reverser gear case, paddies, stripper, front closure sheets, and related components for both standard and Sidehill 6620 combines.
* **Separator Repair:** Explore the cylinder, concave, beater, POSI-TORQ cylinder drive, dual-range cylinder drive, straw walkers, crankshafts, straw chopper, straw spreader, shoe augers, fan, shoe frame, tailings elevator, augers, lower auger, clean grain elevator, and grain tank loading auger.
* **Grain Tank Unloading System Repair:** This section focuses on the grain tank cross augers, vertical auger, bevel gears, and horizontal auger and gears.
* **Major Drives Repair:** Covering the engine powershaft, primary countershaft, and secondary countershaft.
* **Sidehill Leveling System Repair:** Understand the electrical and hydraulic components of the sidehill leveling system, including troubleshooting.
* **Automatic Header Height Control Repair:** This section focuses on the repair of components within the automatic header height control system.
* **Engine Operation and Tests:** Learn about engine operation, system tests, and diagnosis.
* **Fuel and Air System Operation and Tests:** Covering the operation and testing of the air intake system, diesel fuel system, and control linkage.
* **Electrical Operation and Tests:** Understand the general information, diagnosis, and tests for the electrical system, including charging circuit, starting circuit, and lights, instruments, and accessory circuits.
* **Power Train Operation and Tests:** Learn about the diagnosis and testing of the clutch, transmission, final drive, hydrostatic drive systems, 4-wheel drive systems, and Posi-Torq ground drive.
* **Steering and Brakes Operation and Tests:** Explore the operation and testing of the power steering and brakes.
* **Hydraulic Operation and Tests:** Covers the operation and testing of the hydraulic system, including the reservoir, pumps, valves, cylinders, motors, and accumulator.
* **Operator Station Operation and Tests:** Understand the operation and testing of the air conditioning and heating systems.
* **Sidehill Leveling System Operation and Tests:** Covers the general information, diagnosis, and testing of the electrical and hydraulic systems related to sidehill leveling.
* **Automatic Header Height Control Operation and Tests:** Covers general information, diagnosis, and testing of the mechanical, electrical, and hydraulic systems within the automatic header height control system, including the DIAL-A-MATIC system.

This comprehensive service manual provides detailed instructions, diagrams, and specifications, making it an essential resource for anyone working on John Deere 6620, Sidehill 6620, 7720, and 8820 Combines.

The John Deere 6620, Sidehill 6620, 7720, and 8820 combines were powerful and versatile machines designed to tackle a wide range of harvesting tasks. These models represented the pinnacle of agricultural technology during their production years, offering farmers advanced features and capabilities to maximize yields and efficiency. The 6620 series combines featured a robust engine, often a six-cylinder John Deere PowerTech engine, providing ample horsepower for efficient harvesting. The Sidehill 6620, a specialized variant, was designed for harvesting on sloped terrains, incorporating a unique leveling system to maintain stability and optimal combine performance on uneven ground. The larger 7720 and 8820 models boasted even more powerful engines and larger capacities, enabling them to handle heavier workloads and larger fields. These combines were equipped with advanced features like automatic header height control, which ensured consistent cutting height across varying terrain, and a sophisticated threshing system that effectively separated grain from chaff.

The John Deere 6620 series combines were known for their reliability and durability, making them a popular choice among farmers worldwide. These machines were designed and manufactured with high-quality components and rigorous testing, ensuring their ability to withstand demanding conditions. The TM1202 service technical manual served as a comprehensive resource for technicians and operators, providing detailed information on maintenance procedures, troubleshooting, and repair techniques. The manual covered a wide range of topics, from engine and transmission systems to hydraulics, electrical components, and the combine's harvesting mechanisms. This invaluable resource ensured that John Deere 6620 series combines could be kept in optimal working condition, maximizing their lifespan and efficiency across generations of farming.