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Part of the John Deere Repair Manuals.
Every one of the 762 pages in this John Deere 644-B Technical Manual PDF covers one machine: the 644-B wheel loader, from basic engine to loader boom. You get full wiring diagrams with component wire routing, hydraulic schematics for the steering, brake, and loader circuits, and a troubleshooting section built around John Deere's seven basic steps of diagnosis. Inside: torque tables, fluid capacities, and page after page of step-by-step teardown procedures for the transmission, differential, and final drives. When you rebuild the steering valve, torque the cap screws to 35 lb-ft (47 Nm) and remember a full turn of the adjusting screw moves it 0.036 in. (0.9 mm). No more chasing wiring faults with a multimeter and a prayer. Bookmarked with a working text layer; search any spec, jump to any section, and get back on the loader.
What's Inside This John Deere 644B Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 4-48 | Maintenance Without Accident, Complete Page Listing, Predelivery, Delivery, And After-Sale Services |
| Engine | 49-168 | Basic Engine, Connecting Rods and Pistons, Cylinder Block and Cylinder Liners, Crankshaft and Main Bearings, Engine Lubrication System, Engine Cooling System, Fuel System |
| Electrical System | 169-266 | Batteries, Delco Remy Alternator, Motorola Alternator, Delco Remy Starting System, John Deere Starting System, Miscellaneous Electrical Components, Heating and Air Conditioning |
| Power Train | 267-392 | Drive Shafts, Transmission, Turbine Driven Gears and Freewheel Clutch, Output Components and Transfer Driven Gear, Parking Brake and Front Output Flange |
| Hydraulic System | 393-528 | Transmission Pump, Transmission Control Valve, Steering and Brake Pump, Steering Valve, Steering Valve Operation, Brake Valve, Loader Pump |
| Miscellaneous Components | 529-564 | Loader and Engine Frames, Loader Boom and Buckets, Lumber Fork, Canopy and Cabs, Specifications and Special Tools |
| System Testing - Engine and Electrical | 565-629 | Seven Basic Steps of Diagnosis, Visual Inspection, Fuel and Compression Tests, Engine Diagnosis, Starting and Charging Circuit Tests, Return-to-Dig and Boom Raise Circuits, Control Lever Faults |
| System Testing - Heating and Air Conditioning | 630-649 | Air Conditioning Operation and Diagnosis, Refrigerant Charging, Heater and Blower Tests, Compressor and Condenser Checks |
| System Testing - Power Train and Differential | 650-662 | Transmission Diagnosis, Clutch Pressure Tests, Torque Converter Checks, Differential Testing |
| System Testing - Hydraulic, Steering and Brake Systems | 663-732 | Hydraulic System Diagnosis, Steering Valve Tests, Brake System Tests, Loader Hydraulic Tests, Hydraulic System Analyzer, Test Pattern Analysis Chart, Transmission Pump Test |
| System Testing - Specifications and Adjustments | 733-754 | Engine Test Specifications, Hydraulic Pressure Specifications, Heating and Air Conditioning Specifications, Final Adjustments |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Hydraulic oil lines | broken | p. 423 |
| Tighten cap screws | 35 lb-ft (47 Nm) | p. 439 |
| Adjusting screw moves the screw | 0.036 in. (0.9 mm) | p. 438 |
| Every 10 degrees of turn will give a change | 0.001 in. (0.025 mm) | p. 438 |
| Adjust double ball joint (20) (center ball to center ball with studs indexed 180° from each other) | 2.875 in. [73.02 mm] | p. 476 |
| Install washer (30) on stud and tighten | 30 ± 3 lb-ft (41 ± 4 Nm) (4 ± 0.4 kg-m) | p. 476 |
| Battery Cold Cranking Amps (4D) | 800 | p. 251 |
| Engine oil pressure at 1900 rpm | 40 to 50 psi | p. 733 |
John Deere 644B Common Problems This Manual Covers
John Deere 644-B loader boom settles from raised position, bucket drifts down overnight
Raise the boom, shut the engine off, and mark the cylinder rod positions. Drift with the lever centered means internal cylinder leakage or a leaking control valve. Trace the circuit on the hydraulic schematic, reseal the suspect cylinder, and torque valve cap screws to 35 lb-ft (47 Nm), the spec on page 439, on reassembly.
Manual Section: Hydraulic SystemBoom and bucket move slow and jerky first thing on cold mornings
Check hydraulic oil level first; cold or low oil makes the boom hesitate, and fluid capacities are listed on page 16. Run at half throttle until the oil warms, then cycle the boom again. If it stays jerky, inspect the loader pump suction line for air leaks. After any pump work, torque pump cap screws to 170 ± 17 lb-ft (230 ± 23 Nm).
Manual Section: Hydraulic System p. 393Engine cranks slowly or won't turn over at all in cold weather
Load test the batteries before condemning the starter; the 4D battery is rated at 800 cold cranking amps, listed on page 251. Clean and tighten ground and positive connections, then measure voltage drop across the cables during cranking. If the batteries pass, work through the starting circuit tests beginning on page 581.
Manual Section: Electrical System p. 251Hydraulic oil leaking at hose connections, cylinder rods wet after a full day of work
Wipe everything dry, cycle the loader, and find the true source before pulling parts. Check each system for leakage from poor connections and broken hoses using the checklist on page 46. Replace damaged hoses, the long assembly measures 144 in. (3 658 mm), and bleed the power steering valve any time a hydraulic line has been opened.
Manual Section: General p. 46Engine down on power, oil pressure gauge reads low at operating temperature
Verify oil pressure with the engine at normal operating temperature: 40 to 50 psi (3 bar) at 1900 rpm, the spec on page 733. Pressure below that range points to a plugged filter, worn oil pump, or excessive bearing clearance. Check the air intake and fuel transfer pump, then follow the troubleshooting procedures starting on page 571.
Manual Section: Section 70 System Testing - Group 10 Engine p. 733Frequently Asked Questions
What are the torque specifications for the John Deere 644B wheel lug nuts?
The wheel lug nuts for the John Deere 644B loader should be tightened to 300 lb-ft (407 Nm). This specification is found in the installation section for final drives. p. 357
What are the torque specifications for John Deere 644B engine bolts?
For the John Deere 644B engine, cylinder head cap screws require an initial torque of 167 to 197 lb-ft (154 to 226 Nm) and a second pass of 162 to 198 lb-ft (220 to 268 Nm). Connecting rod cap screws are torqued to 55 lb-ft (75 Nm) (7.6 kg-m) plus 90 + 10 – 0°, and main bearing cap screws are set to 210 lb-ft (284 Nm) (29 kg-m). p. 59
What are the replacement specifications for the Quick-connect coupler?
The Quick Coupler Adapter for the John Deere 644B is identified by part number 202850. It is used as part of a 36952 144 in. (3 658 mm) Hose Assembly for hydraulic system tests. p. 730
What are the replacement specifications for Cylinder repair kit (seals)?
The hydraulic cylinders in the John Deere 644B loader use V-packings as seals. When replacing these V-packings, ensure that the apex of the V points away from the barrel and use a suitable ring compressor for proper installation. p. 480
What is the engine oil capacity for the John Deere 644B loader?
The engine oil capacity for the John Deere 644B loader is 2.200 gallons (8.3 liters). This information is provided in the general specifications of the manual. p. 15
What format is this manual in?
Instant PDF download. You get the full 762-page searchable Technical Manual immediately after payment. Open it on your laptop, tablet, or phone right in the shop.
Can I print this manual?
Zero restrictions. The PDF is DRM-free. Print whatever sections you need to take out to the shop. Standard letter or A4 paper works.
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