John Deere JD644C Loader & JD646C Compactor 1984 Technical Manual (P/N TM-1229)

• John Deere Technical Manual TM-1229, revised March 1984, covers the JD644C Loader and JD646C Compactor in a 1,378-page PDF.
• Covers engine removal and internal repair, including crankshaft and main bearings, valve train, connecting rods and pistons, cylinder block, fuel-injection equipment, turbocharger, lubrication, and cooling-system components.
• Details transmission removal and overhaul, power-shift clutch assemblies, transmission controls and hydraulic components, torque converter service, universal joints, differentials, axle shafts, bearings, and planetary reduction gears.
• Separates important machine-specific work: the 644C hydraulic differential lock and rear-axle disconnect linkage, the 646C NO SPIN differential, and the 646C transmission-pump configuration change at serial number 403019.
• Includes steering and brake repair such as steering-valve and metering-pump service, cylinder and accumulator work, relief-valve testing and adjustment, brake-valve repair, brake bleeding, and accumulator charging, plus loader pump, control-valve, boom, bucket, and hydraulic-cylinder service.
• Provides Section 90 system testing with Deere’s seven-step diagnostic method, electrical and hydraulic schematics, component-location drawings, pressure and leakage testing, power-train checks, and heating/air-conditioning diagnosis.

John Deere explicitly states that this technical manual was planned and written for an experienced service technician. That fits the material: TM-1229 assumes normal shop skills and access to lifting equipment, pressure gauges, hydraulic service equipment, and the special tools called out in the repair groups rather than teaching basic mechanical fundamentals.

Drivetrain and Major Component Repair

The transmission coverage goes well beyond removal and installation. It breaks out the reverse-, low-, and high-range power-shift clutch assemblies, output shafts, shifter shaft, transfer drive gear, transmission oil pump, control valve, oil cooler, filter, converter-out check valve, and clutch cut-off solenoid valve. The driveline sections also account for machines fitted with either Mechanics or Rockwell universal joints.

Axle and differential work includes complete differential removal, input-quill and bevel-pinion service, bearing and seal replacement, preload and backlash adjustment, axle-shaft and reduction-gear repair, and post-repair differential-lock testing. Model differences matter here. The 644C uses hydraulic differential-lock coverage and a rear-axle disconnect linkage, while the 646C receives its own NO SPIN differential disassembly, inspection, and assembly procedures. The manual also identifies a 646C transmission-pump drive configuration change at serial number 403019, an important check before selecting parts or test assumptions.

Hydraulic, Steering, Brake, and Loader Systems

The steering section covers the metering pump, steering valve, feedback cylinder, steering cylinders, return filter, accumulator, and emergency-steering hardware. Factory procedures include component removal, disassembly, inspection, assembly, installation, relief-valve testing, pressure adjustment, accumulator charging, and air removal after service.

Service-brake coverage includes the brake elements and pedals as well as the hydraulic brake valve, brake accumulator, inlet check valve, brake bleeding, and accumulator charging. Loader repair sections extend into the hydraulic loader pump, loader control valve, boom and bucket cylinders, multipurpose-bucket cylinder, reservoir, lift linkage, boom, bucket teeth, cutting edges, and related frames.

Diagnostics, Schematics, and Factory Service Data

Section 90 is a dedicated diagnostic section rather than a short troubleshooting appendix. It covers engine cooling, lubrication, fuel, intake-air, compression and oil-pressure checks; starting, charging, lighting, gauges, and indicators; transmission and parking-brake tests; steering, differential-lock, loader-hydraulic, pump-flow, pressure, and cylinder-leakage checks; and heating/air-conditioning diagnosis.

Representative visual references include the Electrical Wiring Diagram, Electrical Schematic, Closed-Center Hydraulic System Schematic, Open-Center Hydraulic System Schematic, the Transmission Control Circuit, and component cross-sections such as the steering return filter and feedback cylinder. The manual also identifies Service-Gard tooling where needed, including the D-05144ST Transmission Adapter Plate, D-05223ST Repair Stand, D-01019AA Hydraulic Hand-Operated Pump, and JDH-46 Pressure Circuit Relief Valve Test Plug.

Factory reference data includes customary and metric hardware torque charts, tube and hose fitting torque tables, component-specific specifications, fluid capacities, pressure-test data, wear and inspection limits, adjustment information, and electrical test values.

Two repair cautions show the level of detail in the manual. Deere specifies that the differential ring gear and spiral bevel pinion shaft are a matched set, so treating either one as an unrelated replacement can leave the gearset mismatched. In steering-valve repair, spool orientation and matched relief-valve parts are controlled because incorrect reassembly can alter operation or pressure settings.

TM-1229 is the actual-service portion of Deere’s two-manual service concept. General theory and fundamental troubleshooting are assigned to FOS manuals, while routine operator servicing and periodic maintenance are covered by the operator’s manual. Because this publication includes raised-loader work, heavy drivetrain assemblies, charged accumulators, and high-pressure hydraulics, follow its lock-bar, lifting, pressure-relief, and electrical-isolation precautions before repair work.