Overview
The AGCO LT75A, LT85A, LT90A and LT95A Tractor Workshop Service Manual provides technical documentation for maintenance, troubleshooting, inspection, adjustment and component repair of these AGCO agricultural tractors. The workshop reference covers tractor separation, engine, clutch, gearbox, rear axle, power take-off (PTO), front axle, hydraulic systems, electrical equipment, electronic controls and cab assemblies. It includes technical information for GBA20 mechanical reverse shuttle and Power Shuttle transmissions, GBA25 gearbox configurations, rear axle assemblies, hydraulic controls and electronic diagnostic systems.
The documentation provides detailed procedures for transmission disassembly, selector mechanism adjustment, synchroniser inspection, shaft shimming, bearing replacement and drivetrain servicing. Additional chapters cover differential and final drive assemblies, PTO clutches, DANA and CARRARO front axles, open-centre and Load Sensing hydraulics, trailer braking, electronic injection, Autotronic 5 controls and Dyna-4 diagnostics. Technical references include operating principles, component diagrams, pressure testing, programming, calibration, error codes, electrical wiring and special service tools. The applicable procedures depend on the tractor’s installed transmission, axle, hydraulic and electronic equipment.
Important Information: The workshop documentation covers several transmission and equipment configurations, including GBA20 mechanical reverse shuttle, GBA20 Power Shuttle, GBA25, alternative front axle assemblies and different hydraulic systems. Confirm the installed components before selecting repair procedures, adjustments or service specifications.
Table of Contents
AGCO LT75A, LT85A, LT90A, LT95A Manual
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01. Introduction and Specifications
- General Workshop Introduction
- Tractor Technical Specifications
- Equipment Identification
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02. Splitting the Tractor
- Front Frame and Cummins Engine Separation
- Front Frame Disassembly and Reassembly
- Front Frame Shimming
- Cummins Engine and GTA2020 Separation
- Engine and Transmission Disassembly and Reassembly
- Input Shaft Seal Replacement — Dry Clutch Configuration
- GBA20/GPA20 Separation with Cab Fixed to Centre Housing
- GBA20/GPA20 Separation with Cab Fixed to Gearbox
- Tractor Separation Service Tools
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03. Engine
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04. Clutch
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05. Gearbox and Transmission
- GBA20 Mechanical Reverse Shuttle Construction and Operation
- GBA20 Mechanical Reverse Shuttle Specifications
- Mechanical Reverse Shuttle Input Unit Removal and Installation
- Reverse Shuttle Operating Principles
- Reverse Shuttle Disassembly and Reassembly
- Reverse Shuttle Secondary Shaft Shimming
- Speedshift Mechanism Construction and Operation
- Speedshift Front Cover Plate Removal
- Speedshift Planet Carrier Disassembly and Assembly
- Speedshift Hydraulic Cover Plate Servicing
- Primary Shaft Needle Roller Bearing Replacement
- Gear Selector Cover Plate Removal and Installation
- Gear Selector and Reverse Shuttle Mechanism Servicing
- Gear Linkage and Reverse Shuttle Control Cable Adjustment
- Selector Rail Maintenance and Inspection
- Creeper Gear Selector Fork
- Hare/Tortoise Range Selector Fork and Lock
- First/Second and Third/Fourth Gear Selector Rails
- Mechanical Reverse Shuttle Selector Fork and Rail
- Output Shaft Disassembly and Assembly
- Output Shaft Bearing Shimming
- Layshaft Disassembly and Reassembly
- Intermediate Shaft and Gear Assembly Removal
- Intermediate Shaft Tapered Roller Bearing Replacement
- Intermediate Shaft Gear and Bearing Shimming
- GBA20 Power Shuttle Construction and Operation
- Power Shuttle Input Unit Removal and Refitting
- Power Shuttle Potentiometer Sensor Adjustment
- Forward Clutch Removal, Disassembly and Assembly
- Forward Clutch Shimming
- Reverse Clutch Disassembly and Assembly
- Power Shuttle Driving Gear and Shaft Adjustment
- Power Shuttle Speedshift Mechanism Servicing
- Power Shuttle Selector Cover Plate and Linkage Adjustment
- Power Shuttle Selector Rail, Output Shaft and Layshaft Servicing
- GBA25 Gearbox Construction and Operation
- GBA25 Transmission Kinematics and Synchronisers
- GBA25 Robotic Mechanical Gearbox Control
- GBA25 PowerShuttle Removal and Installation
- GBA25 Powershift Module Operating Principles
- Powershift Planetary Gear Disassembly and Reassembly
- Robotic Gearbox Primary and Secondary Shaft Servicing
- Robotic Gearbox Shaft Shimming
- Selector Rail, Fork and Interlock Adjustment
- Intermediate Speed Sensor Installation
- GBA20 Creeper Unit Operation and Servicing
- Creeper Planet Carrier and Ring Gear Servicing
- GBA20 Super Creeper Unit
- Super Creeper Epicyclic Gear Train Disassembly
- Super Creeper Control Adjustment
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06. Rear Axle
- GPA20 Centre Housing Construction
- Normal Duty Trumpet Housing Assembly
- Heavy Duty Trumpet Housing Assembly
- Rear Axle Planet Carrier
- Rear Axle Bearings and Seals
- Axle Shaft Bearing Preload Adjustment
- Wheel Stud Replacement
- Rear Axle Brake Piston Disassembly and Assembly
- Handbrake Unit Construction and Operation
- Handbrake Disassembly and Reassembly
- Handbrake Control Assembly and Adjustment
- Rear Axle Differential Construction
- Differential Lock Assembly Removal and Servicing
- Differential Ring Gear Disassembly
- Drive Pinion Removal and Reassembly
- Drive Pinion Taper Distance Adjustment
- Pinion Bearing Shimming
- Differential Assembly Shimming
- Differential Backlash Checking and Adjustment
- Rear Hitch and Linkage Servicing
- Hydraulic Lift Ram Disassembly and Reassembly
- Auto-Hitch Mechanism and Hitch Hook Configurations
- Auto-Hitch Tie-Rod and Control Adjustment
- Dromone Retractable Hitch Operation
- Rear Wheel and Hub Assembly
- Rear Wheel Track Width Adjustment
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07. Power Take-Off (PTO)
- GPA20 PTO Construction and Operating Principles
- PTO Configuration and Type Identification
- PTO Intermediate Shaft, Driving Gears and Brake
- Two-Speed PTO Servicing — Without Shimming
- Two-Speed PTO Servicing — With Shimming
- Four-Speed Economy PTO Servicing — Without Shimming
- Four-Speed Economy PTO Servicing — With Shimming
- Four-Speed Economy PTO Control Adjustment
- Removable PTO Shaft Assembly
- 540 and 1000 rpm PTO Shaft Replacement
- PTO Rear Bearing Disassembly and Assembly
- PTO Gear and Front Bearing Servicing
- Shiftable PTO Shaft Mechanism
- PTO Control and Flanged Shaft
- Reinforced PTO Shaft Sealing
- Ground Speed PTO (GSPTO) Construction and Operation
- Ground Speed PTO Servicing — 2WD Configuration
- Ground Speed PTO Servicing — 4WD Configuration
- PTO Clutch Construction and Operation
- Two-Speed PTO Clutch Removal and Installation
- Four-Speed PTO Clutch Removal and Installation
- PTO Clutch Disassembly and Reassembly
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08. Front Axle
- DANA Front Axle Construction and Specifications
- DANA Final Drive Units
- Planet Carrier, Sun Gear and Ring Gear Servicing
- Wheel Hub Disassembly and Reassembly
- Swivel Housing Shimming
- Universal Joint Shaft Removal and Installation
- DANA Differential Disassembly and Reassembly
- Differential Lock and Drive Pinion Servicing
- Differential Bearing Shimming and Adjustment
- Differential Piston Tightness Testing
- DANA Bearing and Transmission Shaft Servicing
- 4WD GPA20 Clutch Removal and Reassembly
- CARRARO Front Axle Construction and Specifications
- CARRARO Final Drive Unit Disassembly
- CARRARO Wheel Hub and Axle Beam Servicing
- Front Wheel Alignment and Steering Angle Adjustment
- CARRARO Differential and Pinion Servicing
- CARRARO Transmission Shaft and Universal Joint Servicing
- Two-Wheel-Drive Front Axle
- Stub Axle and Wheel Hub Disassembly
- Front Axle Pivot Bearing Servicing
- Steering Ram Removal and Reassembly
- Two-Wheel-Drive Front Axle — Six-Cylinder Configuration
- Front Axle Track Width Adjustment
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09. Hydraulic System
- Open-Centre Hydraulic System — 57 L/min
- Open-Centre Hydraulic System — 100 L/min
- Low-Pressure and High-Pressure Hydraulic Circuits
- Mechanical Reverse Shuttle and Speedshift Hydraulic Circuit
- Power Shuttle and Speedshift Hydraulic Circuit
- Load Sensing Hydraulic System
- Load Sensing Pump and System Operating Principles
- Gearbox and Rear Axle Lubrication Circuits
- Hydraulic Pressure and Flow Testing
- Open-Centre Hydraulic System Testing
- Load Sensing Hydraulic System Testing
- Hydraulic Pump Removal and Reassembly
- Variable Displacement Hydraulic Pump
- Hydraulic Priority Block
- Hydraulic Cover Plate and Valve Servicing
- Hydraulic Pump Seal Replacement
- Brake Master Cylinders — Assisted and Unassisted
- Brake Pedal Adjustment
- Main and Trailer Brake Bleeding
- Bosch Trailer Braking Valve
- Load Sensing Trailer Braking System
- Hydraulic Linkage Spool Valves
- Three-Point Hitch Hydraulic Control
- Auxiliary Hydraulic Spool Valves
- Hydraulic Flow Divider Adjustment
- Low-Pressure Valve Inspection and Adjustment
- Power Shuttle Hydraulic Control Unit
- Speedshift Hydraulic Control
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10. Electrical Equipment
- Cab Electrical Wiring Diagrams
- Engine Electrical Wiring Diagrams
- Transmission Electrical Wiring Diagrams
- Lighting System Electrical Diagrams
- Electronic Controller Power Supply Circuits
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11. Electronic Control Systems and Diagnostics
- Perkins Electronic Fuel Injection Configuration
- Electronic Injection Programming
- Electronic Injection Tests and Diagnostics
- Engine Electronic Injection Error Codes
- Engine Wiring Harness and Controller Diagrams
- Autotronic 5 System Construction and Operation
- Autotronic 5 Controller Connector Identification
- Autotronic 5 Automatic System Responses
- Power Shuttle Electronic Control Principles
- Power Shuttle Programming and Parameter Settings
- Power Shuttle Electronic Tests and Diagnostics
- Autotronic 5 Power Shuttle Error Codes
- Power Shuttle Calibration
- Progressive Shifting Adjustment
- Manoeuvring Pedal and Clutch Pedal Calibration
- Electronic Linkage Construction and Control
- Electronic Hitch Position Sensor Adjustment
- Electronic Linkage Error Codes and Diagnostics
- Electronic Linkage Programming and Calibration
- Autotronic 5 Auto 4 System
- Creeper, Four-Wheel-Drive and Differential Lock Electronic Functions
- Electronic PTO and Transmission Control
- Dyna-4 Programming and Parameter Settings
- Dyna-4 Gearbox and Front Axle Diagnostics
- Dyna-4 Differential and PTO Diagnostics
- Auto 4/Dyna-4 Error Code Analysis
- Power Shuttle and Clutch Pedal Calibration
- Electronic Control Wiring Diagrams
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12. Cab and Equipment
GBA20 Mechanical Reverse Shuttle Synchronisers and Shaft Bearing Adjustment
The GBA20 mechanical reverse shuttle gearbox consists of three gear trains arranged on the layshaft, intermediate shaft and output shaft. The transmission provides eight basic synchronised gear ratios through four forward gear selections and two operating ranges, Hare and Tortoise. Its construction incorporates three single-cone synchronisers, with four synchronised main gearbox gears and a gear mounted to rotate freely on the output shaft. This additional gear is controlled by a synchroniser to provide the two-range arrangement. The gears use helical teeth and remain in constant mesh during operation.
The layshaft and intermediate shaft are supported by tapered roller bearings, while the output shaft uses two tapered roller bearings and one needle roller bearing. Correct bearing adjustment is important during gearbox overhaul. The supplied servicing extract specifies preload for the layshaft and clearance for the intermediate shaft. The output shaft may be adjusted with either slight clearance or slight preload, according to the applicable servicing instructions. When replacing bearings or disassembling the gearbox, follow the documented shaft shimming procedures to maintain the specified assembly conditions rather than applying identical bearing settings to all three shafts.
The workshop documentation also covers alternative Power Shuttle and gearbox configurations, including their respective clutch assemblies, selector mechanisms, planetary components and control systems. These procedures must be selected according to the installed transmission. Mechanical reverse shuttle shaft and synchroniser adjustments should not automatically be applied to a Power Shuttle or GBA25 arrangement simply because the assemblies share related transmission components.
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