John Deere 670A/672A Motor Grader Repair Manual, 1978–1987 (P/N TM-1188)

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John Deere Models Covered & Key Technical Specifications

Models: 670A, 672A

Model Years: 1978–1987 (1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987)

Sub-models / Variants: 670A (6414 engine); 672A (6414 engine; hydrostatic front-wheel drive)

Transmission: Direct-drive full Power Shift with planetary gear reductions, both models

  • Engine displacement: 414 cu. in. (6784 cm3)

  • Engine type: Turbocharged diesel, vertical 6-cylinder, 4-stroke cycle

  • Rated engine speed: 2300 RPM

  • Net flywheel power: 125 hp (93.2 kW)

  • Max torque: 372 lb-ft (504 Nm) at 1300 RPM

  • Cooling system capacity: 7 gal (26.5 L)

  • Electrical system: 24 volt

  • Differential internal assembly variant, both models: S/N 005421 onward

  • HFWD wheel-hub oil seal cups, 672A: S/N 401794 onward

  • Clutch-valve linkage, both models: Through S/N 08636; S/N 08637 onward

  • Direction-selector linkage, both models: Eccentric through S/N 509129; screw arrangement from S/N 509130

  • Transmission case, both models: Through S/N 002355; S/N 002356 onward

  • Clutch-pack and transmission-shaft variants, both models: Through S/N 005298; S/N 005299 onward

  • Transmission oil-pump service variant: 670A from S/N 09363; 672A also covered by the assembly-replacement limitation

  • Transmission accumulator variants, both models: Plug and O-ring from S/N 004856; shim arrangement through S/N 010576; replacement O-ring arrangement from S/N 010577

  • Clutch-valve plug and O-ring variant, both models: S/N 507334 onward

  • Parking-brake caliper retaining hardware, both models: Locknut through S/N 009390; special nut and cotter pin from S/N 009391

  • Engine-frame pivot shims, both models: S/N 505455 onward

  • Seat-support adjusters, both models: Through S/N 007470; S/N 007471 onward

  • Engine side-shield variants, both models: Through S/N 007620; S/N 007621 onward

  • Horn variants, both models: Dual horns through S/N 405835; revised horn arrangement from S/N 405836

  • Main hydraulic pump-drive assemblies, both models: Through S/N 010039; S/N 010040–405856; S/N 405857 onward

John Deere Manual Features & Selected Content Preview

John Deere technical manual TM-1188, revised December 1987, covers repair work on the 1978–1987 670A and 672A motor graders, including the JD672A hydrostatic front-wheel-drive equipment.

PDF Search, Navigation, and Readability

Search, bookmarks, and diagram detail: Embedded OCR supports text searches across the technical sections, with recognition errors in some terms and labels. Section and procedure bookmarks are included; one electrical-specifications subentry opens the drawbar section instead. Wheel-motor pages 0260-3 and 0260-4 appear in reverse order. Small labels in the illustrated starter and alternator test connections are readable with zooming, including terminal numbers and the alternator wire-color key.

One printable English-language, 774-page PDF, including 768 manual pages, front and back covers (2 pages), a dealer revision notice (1 page), and unnumbered blank pages (3 pages).

Drivetrain, HFWD, and Grading-Equipment Repair

This selected content overview is not a complete table of contents. Other topics include engine-enclosure hardware and horn service.

  • Engine and fuel systems: Engine removal and installation, injection-pump timing, fuel-system bleeding, nozzle replacement, and turbocharger service.

  • Power Shift transmission and axles: Clutch-pack and planetary-pack repair, transmission-control adjustments, differential setup, tandem drives, and planetary final-drive service.

  • JD672A front-wheel drive: Hydrostatic pump and wheel-motor overhaul, displacement-control valve service, charge-pump repair, and electro-hydraulic actuator replacement.

  • Steering and brakes: Steering-valve and cylinder repair, wheel-lean controls, wet-disk service brakes, accumulator servicing, and parking-emergency brake adjustment.

  • Electrical components: Alternator component tests, starter testing and diagnosis, wiring-harness and switch service, Weather Pack connector replacement, and instrument checks.

  • Grading equipment: Circle drive gearbox and motor repair, blade-control valves, cylinder rebuilding, circle adjustment, and scarifier and ripper servicing.

  • Service specifications: Lubrication charts, fluid capacities, hydraulic cycle times, pressure checks, wear limits, electrical test values, and component torque tables.

John Deere wrote this manual for experienced service technicians who already understand shop service procedures.

Engine and Fuel-System Repair

The engine section covers the 6414 engine’s removal and installation, along with cooling-system and external fuel-supply work. Injection-pump coverage includes calibration specifications and installation timing; turbocharger and water-pump procedures cover removal and replacement.

Separate publications: Full engine repair requires CTM-4. Internal Roosa Master injection-pump repair is referred to TM-1109. Neither publication is included in this PDF.

The fuel-system instructions flag internal injection-pump damage that can result from turning the pump’s outlet fittings during line work.

Transmission, Differential, and Transfer Drive

Step-by-step clutch-pack instructions cover C1/C2 components and the revised wavy-plate arrangement. The illustrated Testing Planetary Pack procedure checks the assembled pack for piston operation and seal leakage before installation.

Differential work extends to bevel-pinion setup, bearing preload, backlash, and the Tooth Bearing Pattern reference. Tandem-chain, planetary final-drive, transfer-drive housing, and gear-and-bearing procedures support drivetrain repair beyond external adjustments.

Transmission oil-pump limits: On the JD670-A from S/N 09363 and the JD672-A, separately serviceable pump parts are limited to cap screws, packing, the oil seal, and bushing. Other worn or damaged internal parts require pump-assembly replacement.

Main Hydraulics and JD672A Front-Wheel Drive

Serial-specific pump-drive illustrations help match the coupling and support arrangement before parts are selected.

The JD672A material distinguishes early and later wheel-drive assemblies and includes the Exploded View of HFWD Pump. Pump inspection addresses scored valve plates, bearing-plate erosion, and piston-slipper damage. Special tools include the JDG-37-1 servo-cylinder socket and JDG-96 rear-bearing puller.

Main radial-piston pump removal, installation, and specifications are included; complete internal repair requires the separate CTM-7.

Electrical Tests and Diagram Coverage

Separate repair sections address the 42-amp and 50-amp alternators. Illustrations include 42 Amp Alternator Circuit and Alternator Test Connections, alongside component tests for windings, diodes, and regulators. Weather Pack procedures identify the JDG-364 extraction tool.

Diagnostic scope: This repair volume does not include the referenced Section 90 diagnostic groups. Group 9016’s HFWD electrical schematic, startup procedure, and neutral adjustments are outside this file. The included component circuits and test diagrams are not a complete machine wiring-diagram set.

Steering, Brakes, and Grading Equipment

Steering coverage separates front steering, rear articulation, and wheel-lean valves and cylinders. Brake work includes valve repair, accumulator precharging, and mechanical parking-brake components.

Blade service covers lift, tilt, side-shift, and circle-control components, including piston cap seals. Drawbar and draft-frame work, normal-service and heavy-duty scarifiers, and rear-mounted rippers have their own repair procedures.

Frame, Cab, and Air Conditioning

Frame separation and reassembly, articulation pivots, cab hardware, seating, and heating equipment are covered. Component torque tables include tandem-housing fasteners and articulation pivots.

The air-conditioning section includes compressor clutch, pulley, bearing, and seal work, plus leak testing and a Cross Section of Compressor. The basic compressor is replaced as a complete unit, not internally rebuilt. The referenced Group 9031 evacuation and charging procedures are not included.

Its service notes warn that applying the pulley puller directly against the drilled shaft end can damage the compressor internally.

Follow the manual’s blocking, lifting, and pressure-release precautions for the articulated frame, raised attachments, and hydraulic and brake systems.

A Preview of Circle Clearances and HFWD Endplay

Circle adjustment: With the circle resting on its supports, maximum vertical clearance between the wear pads and circle is 0.10 in. The specified sum of horizontal clearances between all circle supports and the circle is 0.03–0.06 in.

JD672A wheel motor: The shaft-endplay adjustment procedure specifies 0.006–0.012 in., with shim selection behind the oil-manifold bearing cup.

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John Deere 670A/672A Motor Grader Repair Manual, 1978–1987 (P/N TM-1188) $27.65