John Deere 770A, 770AH, 772A, 772AH Motor Graders Service Manual (P/N TM-1361)

• Covers John Deere 770A, 770AH, 772A, and 772AH motor graders, with model-specific coverage for the hydrostatic front-wheel-drive equipment used on 772A/772AH machines.
• Official John Deere technical publication TM-1361, May 1987, identified on the manual as formerly TM-1187. Digital PDF: 1,330 pages.
• Documents the 466 cu. in. (7.638 L) turbocharged/intercooled six-cylinder diesel, direct-drive full Power Shift transmission, tandem/final-drive assemblies, steering, brakes, electrical systems, main hydraulics, grading equipment, and Automatic Blade Control where equipped.
• Separates standard-speed HFWD, operating through 1st-4th gears, from the high-speed 1st-6th-gear configuration and covers its pump, wheel motors, electro-hydraulic actuator, flow divider, solenoid manifold, controls, and system tests.
• Provides factory specifications, torque data, fluid requirements, special-tool references, predelivery checks, periodic-service data, and Section 90 system diagnosis rather than maintenance information alone.

Component and System Documentation

The manual goes well beyond external service work. Axle and final-drive coverage includes tandem housings, pivot housings, wheel axles, drive chains, planetary reductions, differential lock components, and powered front-wheel assemblies. Differential repair includes cone-point setup, pinion-shaft adjustment, bearing preload, backlash, and tooth-bearing-pattern checks. The Power Shift section breaks the eight-forward/four-reverse transmission down into C1, C2, and C3 clutch assemblies, B1 through B4 brake units, compound planetary packs, reduction shafts, pumps, control valve, forward/reverse modulator, and clutch-disconnect controls.

Engine coverage includes removal and installation plus internal repair information for the earlier engine configuration: crankshaft and main bearings, valve gear, pistons and connecting rods, cylinder block and liners, cylinder head, oiling and fuel systems, turbocharger, cooling components, and starting motor. A critical scope break applies to the later 6466AT-06 engine, engine serial number 249596 and up: John Deere directs complete engine and fuel-system diagnostic, disassembly, inspection, repair, and assembly work to Component Technical Manual CTM-1. Owners planning an internal overhaul of that later engine need CTM-1 in addition to TM-1361.

Other repair sections cover the transfer drive, steering cylinders and linkage, wet-disk service brakes, parking brake, main hydraulic pump and control valves, blade-lift and rear-steer functions, circle drive gearbox, moldboard/circle support adjustment, lift-arm locking system, scarifier/ripper equipment, heating and air conditioning, and the 24-volt electrical system. The 770AH/772AH material identifies the fuel-injection-pump aneroid solenoid control circuit. Automatic Blade Control coverage includes grade/slope sensing, Honeywell hydraulic manifold variants, electrical diagnosis, linkage checks, and dedicated ABC test procedures.

Specifications and Diagnostic Data

The engine is rated at 160 gross hp and 150 net hp at 2200 rpm with a 14.9:1 compression ratio. Engine lubrication capacity changes by PIN: 20 qt (18.9 L) for PIN 500604-508635 and 26 qt (24.6 L) from PIN 508636 onward. Transmission/hydraulic capacity is 31 gal (117.3 L) on 770A/770AH machines and 41 gal (155.2 L) on 772A/772AH machines; each tandem housing takes 5 gal (18.9 L), while the circle-drive gearbox takes 3 qt (2.8 L). Lubrication data calls for HY-GARD J20A in the transmission/hydraulic, tandem, and HFWD systems above -15°F (-26°C), J20B winter grade below that temperature, and SAE EP90 in the circle-drive gearbox.

The after-sale schedule calls for an engine oil/filter change after the first 100 hours and every 200 hours thereafter; transmission/hydraulic filters are addressed at the first 50-hour service. Test data includes 2300-2400 psi main-hydraulic standby pressure, 1800 psi steering-priority pressure, a 1250 psi brake warning threshold, and 165-185 psi transmission clutch pressure. HFWD specifications include 300 ± 10 psi neutral charge pressure and 5000 ± 200 psi high-pressure relief settings, plus wheel-motor and brake-cavity leakage tests, wheel-speed/aggressiveness adjustment, neutral setup, and startup checks. Hydraulic cycle-time charts cover blade lift, blade and circle side-shift, circle rotation, blade pitch, wheel lean, and rear frame steering.

Special-tool references include D-01078AA HFWD Diagnostic Test Box, D-01080AA Master Hydraulic System Analyzer, D-01084AA Tachometer/Temperature Reader, and D-05289ST ABC Test Box. Electrical diagnosis 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.

Representative views and diagrams include the Cross-Sectional View of Transmission, Instrument Panel Wiring Diagram, Component Wiring Diagram, HFWD Electrical Schematic, Hydraulic Schematic (JD770-A), and ABC System Hydraulic Block Diagram.

Several assembly notes are especially important during major repair work. The tandem wheel-axle housings must return to the correct front/rear position with the eyebolt hole at the top because outer wheel-bearing lubrication depends on correct installation. At the differential, allowing an external pressure/brake-line bulkhead fitting to turn can twist off the internal line. The spiral bevel gear and bevel pinion are treated as a matched set, so replacement and subsequent preload/backlash setup must be handled as a pair.

Because these graders use stored brake-accumulator pressure, high-pressure hydraulics, heavy drivetrain and blade assemblies, and a 24-volt electrical system, follow the manual's safety procedures, relieve system pressure, support raised equipment, and use appropriate lifting equipment before repair work.