Rebuilding a boom or tracing a hydraulic fault goes faster when all 200 pages of the JLG G10-55A, G12-55A service manual PDF (OEM 3126019) sit open on your bench, covering both telehandlers from safety practices through the electrical schematics that close the book. Those schematics take up roughly the last quarter, with circuit breakdowns for the engine start, wiper motor, cab heater, dash switches, and Cummins SAE fault codes. Boom work runs just as deep: section removal, extend and retract chain replacement, wear pad service, and separation adjustment, plus dedicated chapters for the John Deere, Perkins, and Cummins engine options. Set main circuit pressure between 3600 and 3650 psi, then torque the lug nuts to 350 to 400 lb-ft, straight from JLG's own tables. A dead start circuit with no schematic eats your morning. Bookmarks and a live text layer put you on the right circuit in seconds.
What's Inside This JLG G10-55A, G12-55A Manual
| System | Pages | Key Topics |
|---|
| Safety Practices | 9-12 | Introduction, Disclaimer, Operation & Safety Manual, Do Not Operate Tags, Safety Information, Safety Instructions, Safety Decals |
| General Information and Specifications | 13-34 | Replacement Parts and Warranty Information, Torque Charts, Specifications, Fluid and Lubricant Capacities, Service and Maintenance Schedules, Lubrication Schedules |
| Boom | 35-66 | Boom System Component Terminology, Boom System - Four Section, Boom Assembly Maintenance, Complete Boom Removal/Installation, Boom Section Removal/Installation |
| Cab and Covers | 67-76 | Operator’s Cab and Covers Component Terminology, Operator’s Cab, Cab Components, Cab Removal, Cab Installation |
| Axles, Drive Shafts, Wheels and Tires | 77-88 | Axle, Drive Shaft and Wheel Component Terminology, Axle Assemblies, Drive Shafts, Wheels and Tires, Brakes, Towing a Disabled Machine |
| Transmission | 89-98 | Transmission Assembly Component Terminology, Transmission Serial Number, Transmission Specifications and Maintenance Information, Transmission Replacement |
| Engine | 99-116 | Introduction - John Deere, Introduction - Perkins, Introduction - Cummins, Engine Cooling System, Engine Electrical System, Fuel System, Engine Exhaust System, Air Cleaner Assembly |
| Hydraulic System | 117-142 | Hydraulic Component Terminology, Safety Information, Hydraulic Pressure Diagnosis, Hydraulic Circuits, Hydraulic Reservoir, Implement Pump, Control Valves, Hydraulic Cylinders |
| Electrical System | 143-200 | Electrical Component Terminology, Specifications, Safety Information, Fuses and Relays, Electrical System Schematics |
Quick Reference Specifications
| Specification | Value | Page |
|---|
| All Models |
| Steering wheel nut torque | 29-34 lb-ft (39-46 Nm) | p. 70 |
| Wheel lug nut torque | 350-400 lb-ft (475-542 Nm) | p. 87 |
| Main circuit pressure (Before S/N 0160037877) | 3600-3650 psi (248-252 Bar) | p. 122 |
| Pilot circuit pressure (Before S/N 0160037877) | 500-550 psi (34-38 Bar) | p. 122 |
| Lift/Lower Cylinder Head Torque (G12-55A - Before S/N 0160033659 excluding 0160033452) | 550-600 lb-ft (745-813 Nm) | p. 140 |
| Lift/Lower Cylinder Nut Torque (G12-55A - Before S/N 0160033659 excluding 0160033452) | 2850-2900 lb-ft (3864-3932 Nm) | p. 140 |
| Perkins Engine Crankcase Oil Capacity | 7 quarts | p. 27 |
| Cummins Engine Crankcase Oil Capacity | 13.5 quarts | p. 27 |
| Hydraulic Reservoir Capacity | 38 gallons | p. 28 |
| Transmission Capacity with Filter Change | 4 gallons | p. 28 |
| G10-55A |
| John Deere (G10-55A) Engine Crankcase Oil Capacity | 14.3 quarts | p. 27 |
| G12-55A |
| John Deere (G12-55A) Engine Crankcase Oil Capacity | 15.8 quarts | p. 27 |
