Service Manual
Models
G10-55A
G12-55A
3126019
Revised
January 5, 2011
EFFECTIVITY PAGE
3126019 G10-55A, G12-55A i
December, 2003 - A - Original Issue Of Manual
July 16, 2004 - B - Revised Manual
March 11, 2005 - C - Added Main Pump Information
July 7, 2006 - D - Revised Manual
April 19, 2007 - E - Revised pages 2.7, 3.16, 5.11, 6.3, 6.4, 7.10, 8.4, 8.6, 8.20, 9.18 & 9.22.
August 8, 2007 - F - Revised pages 2.7, 7.4, 7.5, 7.6, 7.14, 9.4, 9.9, 9.12, 9.15 & 9.17.
May 1, 2008 - G - Revised Danger, Warning & Caution text and pages 1.4, 2.10, 3.14, 3.15, 3.16, 3.17 & 3.19.
January 5, 2011 - H - Revised page numbers and pages 2-3 thru 2-10, 2-13 thru 2-19, 3-4 thru 3-29, 4-6 thru 4-10, 5-4,
5-5, 5-9 thru 5-11, 6-3, 6-6, 7-6 thru 7-9, 7-11 thru 7-15, 8-3 thru 8-12, 8-14 thru 8-25, 9-5 thru 9-12, 9-15 thru 9-21, 9-23,
9-25 thru 9-28, 9-31, 9-32, 9-34 thru 9-36 & 9-42 thru 9-54.
EFFECTIVITY PAGE
G10-55A, G12-55A 3126019 ii
SECTION CONTENTS
Section Subject Page
G10-55A, G12-55A
i
Section 1
Safety Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2 Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.3 Operation & Safety Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.4 Do Not Operate Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.5 Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.6 Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.7 Safety Decals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Section 2
General Information and Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.1 Replacement Parts and Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.2 Torque Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
2.4 Fluid and Lubricant Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15
2.5 Service and Maintenance Schedules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
2.6 Lubrication Schedules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
Section 3
Boom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.1 Boom System Component Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
3.2 Boom System - Four Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.3 Boom Assembly Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.4 Complete Boom Removal/Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3.5 Boom Section Removal/Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3.6 Extend/Retract Chain Removal/Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16
3.7 Boom Section Separation Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18
3.8 Hose Carrier Assembly Removal/Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
3.9 Quick Switch Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23
3.10 Boom Head - Mounted Winch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24
3.11 Boom Wear Pads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24
3.12 Boom Extend and Retract Chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25
3.13 Forks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-29
3.14 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-30
Section 4
Cab and Covers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.1 Operator’s Cab and Covers Component Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.2 Operator’s Cab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
4.3 Cab Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
4.4 Cab Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4.5 Cab Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
Section Subject Page
ii
G10-55A, G12-55A
Section 5
Axles, Drive Shafts, Wheels and Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.1 Axle, Drive Shaft and Wheel Component Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5.2 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.3 Axle Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.4 Drive Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
5.5 Wheels and Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10
5.6 Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11
5.7 Towing a Disabled machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11
Section 6
Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
6.1 Transmission Assembly Component Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
6.2 Transmission Serial Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
6.3 Transmission Specifications And Maintenance Information . . . . . . . . . . . . . . . . . . . . . . 6-3
6.4 Transmission Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
6.5 Torque Convertor Diaphragm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
6.6 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
Section 7
Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
7.1 Introduction - John Deere. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2
7.2 Introduction - Perkins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4
7.3 Introduction - Cummins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6
7.4 Engine Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8
7.5 Engine Electrical System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10
7.6 Fuel System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10
7.7 Engine Exhaust System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-12
7.8 Air Cleaner Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13
7.9 Engine Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14
7.10 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17
Section 8
Hydraulic System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1
8.1 Hydraulic Component Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2
8.2 Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3
8.3 Hydraulic Pressure Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3
8.4 Hydraulic Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4
8.5 Hydraulic Reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13
8.6 Implement Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14
8.7 Control Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15
8.8 Hydraulic Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-21
Section 9
Electrical System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1
9.1 Electrical Component Terminology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3
9.2 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6
9.3 Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6
9.4 Fuses and Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6
9.5 Electrical System Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-10
9.6 Circuit Breakdowns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-22
Section Subject Page
iii
G10-55A, G12-55A
9.7 Engine Start Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-26
9.8 Window Wiper/Washer Windshield Wiper Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-28
9.9 Cab Heater and Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-30
9.10 Solenoids, Sensors and Senders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-30
9.11 Display Monitor and Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-37
9.12 Dash Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-38
9.13 Troubleshooting - John Deere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-40
9.14 Engine Indicator Lamps - Perkins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-42
9.15 SAE Diagnostic Trouble Codes and Fault Codes - Cummins . . . . . . . . . . . . . . . . . . . . 9-43
Section Subject Page
iv
G10-55A, G12-55A
1-1
G10-55A, G12-55A
Section 1
Safety Practices
Contents
PARAGRAPH TITLE PAGE
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2 Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.3 Operation & Safety Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.4 Do Not Operate Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.5 Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.5.1 Safety Alert System and Signal Words . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.6 Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.6.1 Personal Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.6.2 Equipment Hazards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.6.3 General Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.6.4 Operational Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
1.7 Safety Decals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Safety Practices
1-2
G10-55A, G12-55A
1.1 INTRODUCTION
This service manual provides general directions for
accomplishing service and repair procedures. Following
the procedures in this manual will help assure safety and
equipment reliability.
Read, understand and follow the information in this
manual, and obey all locally approved safety practices,
procedures, rules, codes, regulations and laws.
These instructions cannot cover all details or variations in
the equipment, procedures, or processes described, nor
provide directions for meeting every possible contingency
during operation, maintenance, or testing. When additional
information is desired consult the local distributor.
Many factors contribute to unsafe conditions: carelessness,
fatigue, overload, inattentiveness, unfamiliarity, even
drugs and alcohol, among others. For optimal safety,
encourage everyone to think, and to act, safely.
Appropriate service methods and proper repair
procedures are essential for the safety of the individual
doing the work, for the safety of the operator, and for the
safe, reliable operation of the machine. All references to
the right side, left side, front and rear are given from the
operator’s seat looking in a forward direction.
Supplementary information is available from JLG in the
form of Service Bulletins, Service Campaigns, Service
Training Schools, the JLG website, other literature, and
through updates to the manual itself.
1.2 DISCLAIMER
All information in this manual is based on the latest
product information available at the time of publication.
JLG reserves the right to make changes and
improvements to its products, and to discontinue the
manufacture of any product, at its discretion at any time
without public notice or obligation.
1.3 OPERATION & SAFETY MANUAL
The mechanic must not operate the machine until the
Operation & Safety Manual has been read & understood,
training has been accomplished and operation of the
machine has been completed under the supervision of an
experienced and qualified operator.
An Operation & Safety Manual is supplied with each
machine and must be kept in the manual holder located
in the cab. In the event that the Operation & Safety
Manual is missing, consult the local distributor before
proceeding.
1.4 DO NOT OPERATE TAGS
Place Do Not Operate Tags on the ignition key switch and
the steering wheel before attempting to perform any
service or maintenance. Remove key and disconnect
battery leads.
1.5 SAFETY INFORMATION
To avoid possible death or injury, carefully read,
understand and comply with all safety messages.
In the event of an accident, know where to obtain medical
assistance and how to use a first-aid kit and fire
extinguisher/fire suppression system. Keep emergency
telephone numbers (fire department, ambulance, rescue
squad/paramedics, police department, etc.) nearby. If
working alone, check with another person routinely to
help assure personal safety.
1.5.1 Safety Alert System and Signal Words
DANGER indicates an imminently hazardous situation
which, if not avoided, will result in death or serious injury.
WARNING indicates a potentially hazardous situation
which, if not avoided, could result in death or serious
injury.
CAUTION indicates a potentially hazardous situation
which, if not avoided, may result in minor or moderate
injury.
DANGER
WARNING
CAUTION
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Description
Thank you for considering this Complete Service Repair Workshop Manual for the JLG Telescopic Forklift G10-55A, G12-55A AccuPlace for the years 2009-2016.
This comprehensive manual is designed to assist both professional mechanics and DIY enthusiasts in performing a wide range of service and repair procedures.
With easy-to-follow step-by-step instructions and detailed illustrations, this manual enables you to save on repair costs by completing the tasks yourself.
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