John Deere 670A/672A Motor Grader Full Technical Manual (1987) – 270 Pages | OEM Specs

John Deere 670A and 672A Motor Grader Repair Manual - TM1188 (1987 Edition)

This factory-authorized technical manual provides the definitive engineering data required to maintain the structural integrity and operational uptime of the 670A and 672A series. By utilizing OEM-specified clearances and hydraulic flow rates, technicians eliminate the high cost of downtime caused by "guesswork" repairs, ensuring that every adjustment meets the original durability standards of the 1978-1987 production cycle. This specific December 1987 revision is essential for fleets, as it incorporates critical updates for Weather Pack electrical connectors and the Radial Piston Pump (CTM-7) not found in earlier printings.

Model Range & Powertrain Compatibility

This comprehensive workshop manual provides deep-tier coverage for the following configurations and major components:

• Grader Models: John Deere 670A (Standard Drive) and 672A (All-Wheel Drive / FWD).
• Serial Number Range: Comprehensive coverage for units pre- and post-serial number 010039.
• Engine Systems: John Deere 6-Cylinder 414 cu. in. (6.8L) Turbocharged Diesel (Manual includes CTM-4 Engine Supplement).
• Hydraulic Architectures: Radial Piston Pump systems (Manual includes CTM-7 Supplement) and specific FWD hydrostatic motor circuits for the 672A.

Investment Protection & Operational ROI

• Eliminate Component Failure: Exact torque-to-yield specifications for the engine frame and final drive housing prevent hardware fatigue and expensive casting fractures.
• Precision Hydraulic Tuning: Factory-spec pressure settings for the priority valve and variable displacement pumps ensure responsive steering and moldboard control, reducing operator fatigue.
• Circuit Integrity: Detailed guidance on Weather Pack connector assembly prevents intermittent electrical faults and "ghost" codes that plague older machines.
• OEM Standards: Using factory data instead of generic advice protects the machine's resale value by maintaining a verifiable service history to John Deere standards.

Document Metadata

• Print Number: TM-1188 (Dec-87)
• Total Pages: 270+ (Approximate based on technical density)
• File Format: Searchable Digital PDF

Troubleshooting Intelligence & Diagnostic Logic

The manual utilizes a structured, circuit-by-circuit diagnostic methodology designed to isolate faults within the complex interplay of the grader's hydraulic and mechanical systems. By following the "Theory of Operation" sections before diving into the "Tests and Adjustments," technicians can verify if a performance drop is due to a simple relief valve bypass or a more serious internal pump seal failure. This logical progression transforms reactive "parts swapping" into proactive, data-driven maintenance.

Engineering Schematics & Visual Accuracy

High-resolution technical illustrations provide transparent views of the articulated frame joints, tandem housings, and the intricate 8-speed Power Shift transmission. The hydraulic schematics clearly delineate the FWD motor circuits for the 672A, allowing for precise tracking of oil flow from the variable displacement pump to the reversible wheel motors. These visuals are critical for identifying the exact location of shim points (e.g., Engine Frame Shims 505455) and grease fittings often overlooked in generic guides.

Comprehensive Technical Syllabus

• Section I: General Information (Safety, Torque Values, Lubrication)
• Section 5: Engine Auxiliary Systems (Cooling, Intake, Exhaust)
• Section 10: Electrical System (Wiring Harness, Weather Pack Connectors)
• Section 15: Power Train (Power Shift Transmission, Differentials, Final Drives)
• Section 16: Steering and Brakes (Articulated Frame, Power Steering)
• Section 17: Frame, Chassis, and Moldboard (Main Frame, Blade Support)
• Section 18: Hydraulic System (Main Pump, Valves, Cylinders)
• Section 19: Ground Conditioning Tools (Scarifier and Ripper)

Vital Maintenance Benchmarks

FAQ

Does this manual cover both the standard 670A and the All-Wheel Drive 672A models? Yes, this technical manual provides comprehensive repair data for both the John Deere 670A and 672A Motor Graders. It specifically addresses the 414 cubic inch (6.8L) 6-cylinder turbocharged diesel engine and includes vital serial number breaks, such as updates for units post-serial number 010039. For 672A owners, the manual includes specialized hydrostatic front-wheel drive (FWD) logic and component repair for the reversible 2.03 cubic inch wheel motors, ensuring your AWD system remains synchronized and operational under heavy load.

What is the critical torque specification for the hydraulic cylinder stop nuts? The manual mandates a specific torque range of 600 to 700 lb-ft (813 to 949 Nm) for the cylinder stop nuts. Adhering to this high-torque specification is essential for maintaining the structural integrity of the piston-to-rod connection. Failure to meet these OEM values can lead to the piston loosening during high-pressure grading operations, which often results in catastrophic internal cylinder scoring and expensive hydraulic system contamination.

How does this manual assist in troubleshooting the complex hydraulic systems? This manual utilizes the December 1987 revision data, which integrates the CTM-7 Radial Piston Pump supplement. It provides step-by-step diagnostic logic for the closed-center, pressure-controlled system, including pressure settings for the priority valve and the 5.43 cubic inch variable displacement pump. By following these factory flow-test procedures, technicians can isolate internal leakages or valve bypass issues, preventing the unnecessary and costly replacement of expensive hydraulic pumps.

What specialized tools and procedures are required for frame and pivot maintenance? The manual outlines precise procedures for joining the engine and main frames, specifically highlighting the lower pivot pin installation. It requires a "strike and snug" method where the nut is tightened, the pin is struck with a lead hammer to seat it perfectly, and then the nut is backed off to zero torque before being tightened to a "just snug" position. This exact sequence, combined with the use of specific shims like the 505455 series, is critical to eliminate frame slop and ensure precise moldboard control.

How do the high-resolution schematics improve electrical system repairs? This updated edition includes dedicated sections for Weather Pack electrical connectors and comprehensive wiring harness diagrams. These high-utility schematics allow for pin-by-pin testing of the electrical system, ensuring that connectors are installed at the proper terminals to prevent short circuits. Having these digital schematics on the shop floor allows for instant zooming into connector views, which is vital for identifying intermittent faults in the 1980s-era wiring that generic manuals often overlook.