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

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.

Supplied as one English-language, 774-page PDF.

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

• 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 test connections, 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.

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

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.

Main Hydraulics and JD672A Front-Wheel Drive

Pump-drive illustrations distinguish serial numbers through 010039, 010040–405856, and 405857 onward. These differences help match the coupling and support arrangement before parts are selected.

The JD672A material includes early and later wheel-drive assemblies, wheel-motor shaft endplay adjustment, and 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.

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.

Specifications and Maintenance Data

Reference sections provide fluid capacities, lubrication charts, hydraulic cycle times, pressure checks, wear limits, and electrical test values. Component torque tables include tandem-housing fasteners and articulation pivots.

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

File Format and Readability

The page count includes 768 manual pages, front and back covers (2 pages), the dealer revision notice (1 page), and unnumbered blank pages (3 pages).

Text search: Embedded OCR supports searches across the technical sections, with recognition errors in some terms and labels.

Navigation: Section and procedure bookmarks are included. An electrical-specifications subentry points to the drawbar section; the parent electrical-specifications bookmark opens correctly. Wheel-motor pages 0260-3 and 0260-4 appear in reverse order.

Diagram readability: Small labels in the illustrated starter and alternator test connections are readable with zooming, including terminal numbers and the alternator wire-color key.