John Deere 770A, 770AH, 772A, 772AH Motor Grader Technical Manual — 1978–1987 (P/N TM-1361)

John Deere TM-1361 (May 1987), formerly TM-1187, covers 770A, 770AH, 772A, and 772AH motor graders, including the hydrostatic front-wheel-drive equipment used on 772A/772AH machines.

PDF Search, Bookmarks, and Foldout Diagrams

Search and diagram detail: Embedded OCR supports text search on most pages, but some diagrams and system-operation pages are not searchable. PDF bookmarks cover the repair and diagnostic sections. Small labels on the large wiring schematics require zooming.

Supplied as one printable 1,330-page PDF in English, including the original cover, three unnumbered blank pages, 75 internal blank pages, and the foldout diagrams.

Drivetrain Repair, HFWD Testing, and Blade Control

These selected repair and diagnostic topics illustrate the manual’s coverage. Additional procedures include cab removal and suspension-seat service.

• Engine repair: Engine removal and installation, earlier-engine internal repair, fuel-injection timing, turbocharger service, and cooling-system procedures, with a separate-manual requirement for later engines.

• Power Shift and drivetrain: Transmission disassembly, clutch and planetary-pack repair, differential adjustment, tandem-drive service, and transfer-drive overhaul.

• Hydrostatic front-wheel drive: Standard- and high-speed configurations, pump and wheel-motor repair, electrical/hydraulic fault isolation, leakage tests, and neutral adjustments.

• Hydraulics, steering, and brakes: Main-pump and control-valve repair, pressure and flow testing, steering leakage checks, brake-accumulator tests, and brake bleeding.

• Grading equipment: Circle gearbox repair, moldboard/circle adjustments, blade-float controls, scarifier/ripper service, and Automatic Blade Control diagnosis.

• Electrical and cab systems: Starting and charging tests, instrument and control circuits, wiring diagrams, electrical schematics, and heating/air-conditioning diagnosis.

John Deere wrote this manual for experienced service technicians; basic service theory is covered in separate Fundamentals of Service manuals.

Engine Repair and Serial-Number Limits

Earlier engine: Step-by-step internal repair procedures cover the 6531 engine through engine S/N 249595. They address crankshaft and main bearings, valve gear, pistons and connecting rods, cylinder block and liners, cylinder head, and the oiling system.

Fuel-system procedures cover Roosa-Master Model DM injection-pump removal, installation, and timing, plus injection-nozzle testing and repair. Internal injection-pump repair requires TM-1109, which is not included.

Water-pump, thermostat, oil-cooler, and starting-motor work supplement the turbocharger repair material.

Later engine: For the 6466AT-06 engine, engine S/N 249596 and up, complete engine and fuel-system diagnosis, disassembly, inspection, repair, and assembly require the separate CTM-1 component manual, which is not included. The machine manual retains engine removal/installation and later-engine starter and fan-drive procedures.

Power Shift, Axles, and Final Drives

The direct-drive, eight-forward/four-reverse Power Shift section covers C1, C2, and C3 clutch assemblies, B1 through B4 brake units, compound planetary packs, and reduction shafts. The Cross-Sectional View of Transmission identifies the internal assemblies.

Hydraulic-control coverage includes transmission pumps, the control valve, forward/reverse modulator, and clutch-disconnect controls.

Axle and final-drive material covers tandem housings, pivot housings, wheel axles, drive chains, planetary reductions, differential-lock components, and powered front-wheel assemblies.

Differential setup: Repair instructions address cone-point setup, pinion-shaft adjustment, bearing preload, backlash, and tooth-bearing-pattern checks. The spiral bevel gear and bevel pinion are supplied as a matched set.

The assembly notes explain how incorrect tandem wheel-axle housing orientation can interrupt outer-bearing lubrication. At the differential, a turning pressure/brake-line bulkhead fitting can twist off the internal line.

HFWD Variants and Fault Isolation

Standard-speed HFWD operates through 1st–4th gears; the high-speed configuration operates through 1st–6th. Different pumps and planetary drives are documented alongside the electro-hydraulic actuator, flow divider, and solenoid manifold.

The propel-motor identification notes distinguish E for standard-speed equipment and F for high-speed equipment. This helps match the HFWD configuration before selecting parts or repair procedures.

Section 90 combines the HFWD Electrical Schematic with startup checks, wheel-motor and brake-cavity leakage tests, wheel-speed/aggressiveness adjustment, and pump/actuator neutral setup. Electrical testing references the D-01078AA HFWD Diagnostic Test Box.

Hydraulics, Grading Equipment, and Blade Control

Repair sections address steering cylinders and linkage, wet-disk service brakes, and the mechanical parking brake. Diagnostic data covers standby and steering-priority pressures, brake-warning and accumulator checks, transmission clutch pressure, and HFWD charge/relief-pressure testing.

Grading material extends to blade-lift and rear-steer functions and the lift-arm locking system. Hydraulic cycle-time charts cover blade lift, blade and circle side-shift, circle rotation, blade pitch, wheel lean, and rear frame steering.

The Hydraulic Schematic (JD770-A) shows the main circuit. Automatic Blade Control material addresses grade/slope sensing, Honeywell manifold variants, linkage checks, and electrical diagnosis.

The ABC System Hydraulic Block Diagram and D-05289ST ABC Test Box support fault isolation. Dedicated electrical tests cover sensors, valves, the slope-control unit, and wiring; hydraulic faults are investigated using the vehicle hydraulic-system tests.

Electrical Diagnosis and Service Data

The 24-volt electrical material covers starting and charging circuits, 42- and 50-amp alternator tests, gauge/indicator circuits, auxiliary hydraulic controls, air-conditioning circuits, wire routing, and a complete electrical schematic.

The Instrument Panel Wiring Diagram and Component Wiring Diagram supplement circuit diagnosis. The 770AH/772AH material identifies the fuel-injection-pump aneroid solenoid control circuit.

Maintenance references: Predelivery checks and initial and recurring engine-oil/filter and transmission/hydraulic-filter schedules accompany component-specific torque tables, wear limits, fluid capacities, and electrical test specifications.

Capacity tables distinguish engine-oil requirements at PIN 508636 and transmission/hydraulic requirements between 770A/770AH and 772A/772AH machines.

Lubrication data lists HY-GARD J20A for tandem drives, J20A/J20B temperature-dependent applications for transmission/hydraulic and HFWD systems, and SAE EP90 for the circle-drive gearbox.

Hydraulic and transmission testing references the D-01080AA Master Hydraulic System Analyzer and D-01084AA Tachometer/Temperature Reader.

Because these graders use stored brake-accumulator pressure, high-pressure hydraulics, and heavy drivetrain and blade assemblies, follow the manual’s safety procedures, relieve system pressure, support raised equipment, and use appropriate lifting equipment before repair work.

Valve-Clearance and Camshaft End-Play Examples

For the earlier 6531 engine, the valve-clearance adjustment section specifies 0.015 ± 0.002 in. for intake valves and 0.025 ± 0.002 in. for exhaust valves. These settings apply with the engine hot or cold.

Camshaft inspection data distinguishes new-part end play of 0.004–0.010 in. from the maximum allowable end play of 0.0150 in.