Part of the John Deere Repair Manuals.
Grain is standing, the combine is down, and the dealer can't get out until next week. This is the John Deere technical manual for the 6620, Sidehill 6620, 7720 and 8820 combines.
Repair sections cover the engine, fuel and air, electrical, power train, Sundstrand and Eaton hydrostatic drives, Posi-Torq drive, steering, brakes and hydraulics. They also cover the cab, headers, feeder house, separator, cleaning shoe, grain tank and unloading augers. Operation and Tests sections add color wiring diagrams, hydraulic schematics, pressure tests and Diagnosing Malfunctions charts.
These diesels use mechanical injection and set no fault codes. Gauge readings and the malfunction charts are how you find the problem.
What's Inside This John Deere 6620, Sidehill 6620, 7720, 8820 Manual
| System | Pages | Key Topics |
|---|---|---|
| Cover and Contents | 1-8 | Contents and Section Tabs |
| General | 9-30 | Serial Numbers, Specifications, Speeds, Dimensions, Diagnosing and Testing, Tune-Up and Adjustment |
| Engine Repair | 31-116 | Cylinder Head, Valves and Camshaft, Block, Liners, Pistons and Rods, Crankshaft and Main Bearings, Lubrication, Cooling |
| Fuel and Air Repair | 117-190 | Air Intake, Diesel Fuel System, Speed Control Linkage |
| Electrical Repair | 191-270 | Charging, Starting, Lights and Instruments |
| Clutch, Transmission and Final Drive Repair | 271-354 | Clutch, Transmission, Differential, Final Drive |
| Sundstrand Hydrostatic Drive Repair | 355-422 | Drain and Refill, Flushing, Pump and Motor |
| Eaton Hydrostatic Drive Repair | 423-498 | Drain and Refill, Pump, Motor, Oil Cooler |
| Four-Wheel Drive, Posi-Torq Drive and Tires | 499-606 | Planetary Four-Wheel Drive, Cam Lobe Motor, Posi-Torq Drive, Tires and Wheels |
| Steering and Brakes Repair | 607-654 | Power Steering, Brakes |
| Hydraulic Repair | 655-718 | Reservoir, Pumps, Valves, Cylinders, Motors, Accumulator |
| Separator Shell and Operator Station Repair | 719-796 | Separator Shell, Cab, Air Conditioning, Pressurizer, Heater, Seat |
| Header Repair | 797-866 | 200 and 900 Series Cutting Platforms, 40 Series Corn Heads, Row-Crop Heads |
| Feeder House Repair | 867-960 | Conveyor Chain, Drum, Drives and Reverser, Variable Speed Drives, Beaters |
| Separator and Cleaning Repair | 961-1120 | Cylinder, Concave and Beater, Posi-Torq and Dual-Range Cylinder Drives, Straw Walkers, Chopper and Spreader, Shoe, Augers, Fan, Tailings |
| Grain Tank Unloading and Main Drives | 1121-1178 | Cross Augers, Vertical and Horizontal Unloading Augers, Grain Tank, Main Drives, Countershafts |
| SideHill Leveling and Header Height Control Repair | 1179-1206 | SideHill Leveling System, Automatic Header Height Control |
| Engine and Fuel Operation and Tests | 1207-1266 | Engine Operation and Tests, Fuel and Air System Tests, Diagnosing Malfunctions |
| Electrical Operation and Tests | 1267-1410 | Wiring Diagrams, Circuit Diagnosis, Charging, Starting, Lights and Instruments |
| Power Train Operation and Tests | 1411-1532 | Clutch, Transmission, Final Drive, Hydrostatic Drive Tests and Diagnosis, Four-Wheel Drive, Posi-Torq |
| Steering, Brakes and Hydraulic Operation and Tests | 1533-1704 | Power Steering, Brakes, Hydraulic System Operation and Tests |
| Operator Station Operation and Tests | 1705-1764 | Air Conditioning, Pressurizer, Heater |
| SideHill Leveling Operation and Tests | 1765-1806 | Leveling System Electrical and Hydraulic Operation and Tests |
| Header Height Control Operation and Tests | 1807-1922 | Automatic Header Height Control Mechanical, Electrical and Hydraulic Tests, Dial-A-Matic |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Valve clearance, intake / exhaust | 0.018 in. (0.46 mm) / 0.028 in. (0.71 mm) | p. 33 |
| Cylinder head cap screws, grade F | 105 ft-lbs (142 N-m), retighten to 150 ft-lbs (204 N-m) after 1/2 hr at 2100 rpm | p. 59 |
| Cylinder head cap screws, grade G, initial / final | 165 ft-lbs (224 N-m) / 180 ft-lbs (245 N-m) | p. 59 |
| Connecting rod cap screws | 55 ft-lbs (75 N-m), then an additional 1/4 turn (90 degrees) | p. 80 |
| Main bearing caps torque | 150 ft-lbs (203 N-m) | p. 35 |
| Engine oil pressure | 40 to 50 psi (2.75 to 3.75 bar) | p. 36 |
| Thermostat opening temperature | 160 to 180°F (71 to 82°C) | p. 36 |
| Fuel tank, 6620 and Sidehill 6620 / 7720 and 8820 | 82 U.S. Gallons (311 L) / 100 U.S. Gallons (379 L) | p. 119 |
| Fast idle / slow idle | 2340 RPM / 1200 RPM | p. 120 |
| Injection nozzle opening pressure, new: 6620 6466DH-01 / other engines | 3800 psi / 4050 psi | p. 120 |
| Hydraulic system capacity, 6620, 7720, 8820 / Sidehill 6620 | 24 U.S. Qts. (22.8 L) / 31 U.S. Qts. (28.5 L) | p. 656 |
| Main hydraulic relief at 2340 rpm: 7720 / 8820 with 1243 or 1253A headers | (155 bar) 2250 psi / (173 bar) 2500 psi | p. 1544 |
| Steering circuit relief, 8820 and 6620 with two steering cylinders | (119 bar) 1750 psi | p. 607 |
| Hydrostatic high-pressure relief, by serial number | 5300 psi (360 bar) / 5800 psi (394 bar) | p. 1412 |
| Hydrostatic charge pressure | 160 to 180 psi (11 to 12 bar) | p. 1413 |
| Hydrostatic system capacity | 30 U.S. Qts. (28.40 L) | p. 1413 |
| Straw walker / straw chopper speed | 157 rpm / 2360 rpm | p. 963 |
| Cleaning fan speed, 6620 and Sidehill 6620 | 272-965 rpm | p. 963 |
| Dual-Range cylinder drive, slowest range | 160 to 250 rpm | p. 1034 |
| Standard tires, 6620 and Sidehill 6620 / 7720 / 8820 | 23.1-26-in. / 24.5-32-in. / 30.5-32-in. | p. 18 |
John Deere 6620, Sidehill 6620, 7720, 8820 Common Problems This Manual Covers
Correct cylinder speed cannot be reached (Posi-Torq cylinder drive)
Recheck the upper and lower sheave gaps, as the Posi-Torq cylinder drive procedure in Separator and Cleaning Repair explains. If the cylinder runs too slow, either the upper gap is too wide, so remove shims, or the lower gap is too narrow, so adjust the intermediate drive belt. If it runs too fast, either the upper gap is too narrow, so add shims, or the lower gap is too wide, so adjust the intermediate drive belt.
Manual Section: Separator and Cleaning Repair p. 999Cylinder will not change speed (Posi-Torq cylinder drive)
The chart lists three causes. First check the orifice in the main control valve and clean it if it is plugged. Next, trace the hydraulic lines for a leak or restriction. If both check out, the main hydraulic system is not developing the required pressure. Run the relief test in Steering, Brakes and Hydraulic Operation and Tests.
Manual Section: Separator and Cleaning Repair p. 999Combine hesitates when the speed range lever is moved in one direction but responds well in the other (hydrostatic drive)
This points to a defective high pressure relief valve, a defective check valve or a defective directional control valve. Take the gauge readings in the hydrostatic drive tests and diagnosis portion of Power Train Operation and Tests first. Then make the repair in Sundstrand Hydrostatic Drive Repair or Eaton Hydrostatic Drive Repair, depending on which drive your combine has.
Manual Section: Power Train Operation and Tests p. 1453Engine starts and stops
Work through the Diagnosing Malfunctions chart in Engine and Fuel Operation and Tests. If there is air in the fuel system, correct the cause and bleed the system. Replace a clogged fuel filter and clean any clogged or restricted fuel lines. If there is water in the fuel, drain it and install new filters. The diesel fuel system procedures are in Fuel and Air Repair.
Manual Section: Engine and Fuel Operation and Tests p. 1238Frequently Asked Questions
Does this manual cover my John Deere 6620, Sidehill 6620, 7720 or 8820 combine?
Yes. It is the John Deere technical manual for the 6620, Sidehill 6620, 7720 and 8820 combines, with Repair and Operation and Tests sections for each system. It also covers the 200 and 900 Series cutting platforms, 40 Series corn heads, row-crop heads, the SideHill leveling system and automatic header height control. p. 3
What are the John Deere 6620, 7720 and 8820 valve clearances and head bolt torques?
Set intake valves at 0.018 in. (0.46 mm) and exhaust at 0.028 in. (0.71 mm). Grade F head cap screws go to 105 ft-lbs (142 N-m). Retighten them to 150 ft-lbs (204 N-m) after 1/2 hr at 2100 rpm. Grade G cap screws take 165 ft-lbs (224 N-m) initial and 180 ft-lbs (245 N-m) final. Torque connecting rod cap screws to 55 ft-lbs (75 N-m), then turn them an additional 1/4 turn. p. 33
What are the John Deere 6620, 7720 and 8820 combine hydraulic relief pressures and capacities?
Check main hydraulic relief at 2340 rpm fast idle. It is 2250 psi (155 bar) on the 7720 and 2500 psi (173 bar) on the 8820 with 1243 or 1253A headers. Steering circuit relief is 1750 psi (119 bar) on the 8820 and on the 6620 with two steering cylinders. Hydraulic system capacity is 24 U.S. Qts. (22.8 L), or 31 U.S. Qts. (28.5 L) on the Sidehill 6620. p. 1544
What are the John Deere 6620, 7720 and 8820 hydrostatic drive pressures and how are they checked?
Charge pressure should read 160 to 180 psi (11 to 12 bar). High-pressure relief is 5300 psi (360 bar) or 5800 psi (394 bar) depending on serial number, so check your serial number before you test. System capacity is 30 U.S. Qts. (28.40 L). The hydrostatic drive tests and diagnosis section has you take pressure readings with gauges before you go to the malfunction charts. p. 1412
What is inside this manual: wiring diagrams, hydraulic schematics, diagnosis, overhaul?
All of those. There are Repair sections for the engine, fuel system, electrical, transmission, Sundstrand and Eaton hydrostatic drives, four-wheel drive, steering, brakes, hydraulics and cab. Headers, feeder house, separator, cleaning shoe, grain tank and unloading augers are covered too. Operation and Tests adds color wiring diagrams, the overall hydraulic schematic, hydrostatic drive schematics, pressure tests and Diagnosing Malfunctions charts. p. 1280
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