1980 John Deere JD770 Motor Grader Technical Manual (P/N TM-1123)

This John Deere Technical Manual (P/N TM-1123), carrying Deere & Company's 1980 copyright notice, covers maintenance, assembly, repair, and system testing for the JD770 motor grader.

PDF Search, Bookmarks, and Foldout Diagrams

Text search and diagram detail: Text searches work across the main service sections, and embedded PDF bookmarks provide section and component navigation. Several illustrated pages and diagrams lack searchable text. Small wiring numbers and the dense ABC electrical schematic require magnification for clear reading.

One English-language, printable PDF contains 952 pages, including two cover pages and 74 blank or header-only pages.

Power Train, Blade Hydraulics, and System Testing

This selection of service topics previews the manual's coverage; cold-weather starting aids and cab-heater service are among the additional subjects.

• Engine repair: Internal engine overhaul, cylinder-head and valve work, turbocharger inspection, and fuel-injection pump removal, installation, and timing.

• Power train: Power Shift clutch-pack and planetary-pack overhaul, transfer-drive service, tandem-drive repair, differential bevel-drive adjustments, and transmission testing.

• Steering and brakes: Articulated-frame steering, wheel-lean components, wet-disk service brakes, accumulator repair and nitrogen charging, brake bleeding, and parking-brake adjustment.

• Blade hydraulics: Main hydraulic pump repair, blade-lift and circle-control valves, rotary manifold service, cylinder overhaul, and circle gearbox disassembly and assembly.

• Ground-conditioning equipment: Scarifier shanks, rear-mounted ripper frames and cylinders, poppet-valve repair, and two- and three-function snow-wing electrical controls.

• Automatic Blade Control: Mechanical linkage adjustment, slope-control leveling, grade and slope checks, servovalve diagnosis, and electrical component testing.

• Electrical systems: Starting- and charging-circuit diagnosis, alternator and regulator tests, instrument checks, wiring diagrams, and hydraulic-control switch and solenoid testing.

Written for experienced service technicians, the manual provides machine-specific service information and refers to separate Fundamentals of Service manuals for background theory.

Engine Service and Fuel-Injection Repair Limits

Step-by-step instructions cover engine removal and installation, crankshaft and main-bearing work, piston and liner service, and cylinder-head repair. Illustrated tightening sequences and staged cylinder-head torque data accompany valve-clearance and turbocharger checks.

The Roosa-Master DM fuel section includes pump timing and bleeding, plus KDL nozzle disassembly, opening-pressure, leakage, and spray-pattern tests. Internal injection-pump repair is referred to separate manual TM-1109, which is not included.

Tandem Drives and Hydraulic Fault Diagnosis

The Cross-Sectional View of Transmission identifies the clutch and planetary-pack components. Tandem-drive instructions cover axle housings, drive chains, and planetary final drives; differential work includes bearing preload, backlash, and cone-point adjustments.

When tracking down a hydraulic fault or pulling the tandem drive, the factory diagrams and adjustment data provide a common reference for diagnosis and reassembly. The Block Diagram of Transmission Control Circuit and pressure/flow tests connect charge, cooling, lubrication, and clutch complaints with specific test points.

The transmission short test provides an initial diagnosis; a separate complete test includes recorded pressure traces, leakage calculations, and analysis of the results.

Blade Valves and Automatic Grading Controls

Individual blade-control poppet assemblies can be repaired with the valve housing installed. The manual warns that excessive torque on the special plugs can break the Loctite seal on the left-hand-threaded cap or damage the valve body.

The ABC System Hydraulic Block Diagram and individual schematics distinguish Honeywell manifold assemblies 24400059-004, 24400059-007, and 24400059-012. Linkage documentation covers the circle chain, grade-height jack, and bail assembly. Slope-control leveling precedes linkage adjustment, with checks for over- and under-compensation.

D-05289ST ABC Test Box procedures address resistance, continuity, and ground faults in sensors, valves, and interconnecting wiring.

Wiring References and Workshop Precautions

Instrument Panel Wiring, main and secondary harness views, and wire-number/color tables support circuit tracing. The Complete Automatic Blade Control System Electrical Schematic shows sensor, amplifier, and servovalve connections. A subject index directs readers to the relevant service groups.

Working on heavy earthmoving equipment involves significant physical hazards. Always rely on the complete original OEM documentation and standard safety protocols before initiating hands-on teardown or maintenance, particularly around raised implements and stored hydraulic or accumulator pressure.

Capacity and Turbocharger Inspection Examples

The capacity tables specify 31 U.S. gallons for the transmission-hydraulic system, including approximately 8 gallons in cylinders, lines, filters, and related components. Engine lubrication capacity is 22 U.S. quarts including the filter.

For the AiResearch T-04 turbocharger, the axial bearing inspection specifies 0.001–0.004 in. of end play. The same section describes a separate radial-bearing test.