Overview
The Kubota STW34, STW37 and STW40 Tractor Workshop Service Manual provides technical documentation for maintenance, troubleshooting, inspection and component repair of these Kubota compact tractors. The workshop reference covers engine lubrication, cooling and fuel systems, clutch, hydrostatic transmission (HST), Bi-Speed Turn system, independent power take-off (PTO), rear axle, brakes, front axle, power steering, three-point hitch hydraulics, electrical equipment and cabin components. Its mechanism and servicing sections provide component construction, operating principles, technical specifications, checking, adjustment, disassembly and repair procedures.
The documentation includes HST pump and motor operation, cruise control, hydraulic clutch servicing, PTO drive mechanisms, steering controller inspection and hydraulic pump testing. The Bi-Speed Turn system is covered through its hydraulic circuit, control valve, clutch components and electronic diagnostic functions. Separate ROPS and cabin servicing references address equipment removal, electrical wiring and starting systems, while the Cabin chapter provides air-conditioning, refrigeration and windshield component procedures. General information includes maintenance schedules, lubricants, tightening torques, tyre specifications and special service tools.
Notice: The workshop documentation distinguishes ROPS and cabin configurations, including separate engine removal, clutch separation, electrical wiring and starting-system references. Bi-Speed Turn and independent PTO components are also documented through their respective mechanical, hydraulic and electrical sections. Confirm the installed equipment before selecting servicing procedures or technical specifications.
Table of Contents
Kubota STW34, STW37, STW40 Manual
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01. Information and Safety
- Safety First and Workshop Safety Instructions
- Tractor Safety Decals and Warning Labels
- Tractor Technical Specifications
- Tractor Travelling Speeds
- Machine Dimensions
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02. General Information and Maintenance
- Tractor Identification
- General Workshop Precautions
- Electrical Wiring and Component Handling Precautions
- Battery, Fuse and Electrical Connector Handling
- Circuit Tester Precautions
- Electrical Wiring Colour Identification
- Lubricants, Fuel and Coolant Requirements
- General Fastener and Stud Bolt Tightening Torques
- Hydraulic Hose Fitting Tightening Torques
- Hydraulic Pipe Cap Nut Tightening Specifications
- Hydraulic Adaptors and Elbow Fitting Torques
- Metric Screw, Bolt and Nut Specifications
- UNC and UNF Threaded Fastener Specifications
- Plug Tightening Torques
- Tractor Maintenance Checklist
- Daily Inspection and Maintenance
- Initial 50-Hour Maintenance
- Periodic Maintenance — Every 50 Hours
- Periodic Maintenance — Every 100 Hours
- Periodic Maintenance — Every 200 Hours
- Periodic Maintenance — Every 400 Hours
- Periodic Maintenance — Every 600 Hours
- Periodic Maintenance — Every 800 Hours
- Annual Maintenance Requirements
- Two-Year Maintenance Requirements
- Additional Maintenance and Service Checks
- Special Service Tools for Engine Repair
- Special Service Tools for Tractor Components
- Tyre Inflation Pressure
- Front and Rear Wheel Tread Adjustment
- Liquid Tyre Ballast
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03. Engine — Mechanism and Servicing
- Engine Lubricating System Construction
- Engine Cooling System Construction
- Engine Fuel System Construction
- Engine Troubleshooting
- Engine Servicing Specifications
- Engine Tightening Torques
- Engine Body Checking and Adjustment
- Engine Lubricating System Inspection
- Cooling System Checking and Adjustment
- Fuel System Checking and Adjustment
- Engine Separation from Tractor — ROPS Configuration
- Engine Separation from Tractor — Cabin Configuration
- Cylinder Head and Valve Disassembly
- Timing Gear, Camshaft and Fuel Camshaft Disassembly
- Piston and Connecting Rod Disassembly
- Crankshaft Disassembly and Assembly
- Thermostat and Water Pump Disassembly
- Cylinder Head and Valve Inspection and Servicing
- Timing Gear, Camshaft and Fuel Camshaft Servicing
- Piston and Connecting Rod Inspection and Servicing
- Crankshaft Inspection and Servicing
- Engine Cylinder Inspection and Servicing
- Engine Oil Pump Servicing
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04. Clutch — Mechanism and Servicing
- Clutch Linkage Mechanism
- Clutch System Troubleshooting
- Clutch Servicing Specifications
- Clutch Tightening Torques
- Clutch Checking and Adjustment
- Engine and Clutch Housing Separation — ROPS Configuration
- Engine Separation Preparation — Cabin Configuration
- Clutch Disassembly and Assembly
- Clutch Component Inspection and Servicing
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05. Transmission, Hydrostatic Drive and Bi-Speed Turn
- Transmission Construction and Structure
- Hydrostatic Transmission (HST) Construction
- HST Hydraulic Circuit
- Hydrostatic Pump and Motor
- HST Operating Principles and Control Valves
- Hydrostatic Transmission Control Linkage
- Cruise Control Linkage
- Cruise Control Release System
- Range Gear Shift Mechanism
- Front-Wheel-Drive Transmission Section
- Bi-Speed Turn System Features
- Bi-Speed Turn Component Arrangement
- Bi-Speed Turn Hydraulic Oil Flow
- Bi-Speed Hydraulic Clutch Power Train
- Independent PTO System
- Independent PTO Hydraulic Oil Flow
- Hydraulic PTO Clutch Power Train
- Rear PTO Gear Shift Section
- Mid-PTO Gear Shift Section
- Transmission Troubleshooting
- Transmission Servicing Specifications
- Transmission Tightening Torques
- HST and Transmission Checking and Adjustment
- Engine and Clutch Housing Separation
- Clutch Housing Case Separation
- Hydrostatic Transmission Removal
- Transmission Mid Case Separation
- Transmission Case Separation
- Clutch Housing Case Disassembly and Assembly
- Hydrostatic Transmission Disassembly and Assembly
- Mid Case Disassembly and Assembly
- Transmission Case Disassembly and Assembly
- Bi-Speed Hydraulic Clutch and Gear Servicing
- Hydraulic PTO Clutch and Gear Servicing
- Transmission Case Inspection and Servicing
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06. Rear Axle — Mechanism and Servicing
- Rear Axle Construction
- Rear Axle Final Reduction System
- Rear Axle Troubleshooting
- Rear Axle Servicing Specifications
- Rear Axle Tightening Torques
- Rear Axle Separation — ROPS Configuration
- Rear Axle Separation — Cabin Configuration
- Rear Axle Disassembly and Assembly
- Rear Axle Component Inspection and Servicing
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07. Brakes — Mechanism and Servicing
- Brake Linkage Mechanism
- Brake System Operating Principles
- Brake System Troubleshooting
- Brake Servicing Specifications
- Brake Tightening Torques
- Brake Checking and Adjustment
- Rear Axle Separation for Brake Servicing — ROPS Configuration
- Rear Axle Separation for Brake Servicing — Cabin Configuration
- Brake Component Inspection and Servicing
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08. Front Axle — Mechanism and Servicing
- Front Axle Construction
- Front Axle Troubleshooting
- Front Axle Servicing Specifications
- Front Axle Tightening Torques
- Front Axle Checking and Adjustment
- Front Axle Assembly Separation
- Front Axle Disassembly and Assembly
- Front Axle Component Inspection and Servicing
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09. Power Steering System
- Steering System Construction
- Power Steering Hydraulic Circuit
- Power Steering Hydraulic Pump
- Steering Controller Construction
- Steering Control Valve
- Steering Metering Device (Gerotor)
- Steering Controller Hydraulic Oil Flow
- Power Steering Cylinder
- Steering System Troubleshooting
- Steering Servicing Specifications
- Steering Tightening Torques
- Steering System Checking and Adjustment
- Steering Controller Disassembly and Assembly
- Power Steering Cylinder Disassembly and Assembly
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10. Hydraulic System and Three-Point Hitch
- Hydraulic System Construction
- Complete Tractor Hydraulic Circuit
- Hydraulic Pump Construction
- Hydraulic Regulator Valve
- Bi-Speed Hydraulic Valve
- Bi-Speed Valve Hydraulic Circuit
- Bi-Speed Valve Hydraulic Oil Flow
- Three-Point Hitch Hydraulic System
- Three-Point Hitch Hydraulic Circuit
- Three-Point Hitch Feedback Linkage
- Position Control Valve
- Hydraulic Relief Valve
- Three-Point Hitch Hydraulic Cylinder
- Hydraulic Block-Type Outlet
- Auxiliary Hydraulic Control Valve
- Auxiliary Hydraulic Circuit
- Hydraulic System Troubleshooting
- Hydraulic Servicing Specifications
- Hydraulic Tightening Torques
- Power Steering Hydraulic Pump Checking and Adjustment
- Three-Point Hitch Hydraulic Pump Checking and Adjustment
- Hydraulic Regulator Valve Checking
- Three-Point Hitch Hydraulic System Checking
- Hydraulic Pump Disassembly and Assembly
- Bi-Speed Hydraulic Valve Disassembly and Assembly
- Position Control Valve Disassembly and Assembly
- Hydraulic Cylinder Cover Disassembly
- Three-Point Hitch Hydraulic Cylinder Disassembly
- Auxiliary Control Valve Disassembly and Assembly
- Hydraulic Pump Component Inspection and Servicing
- Hydraulic Cylinder Inspection and Servicing
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11. Electrical System and Bi-Speed Turn Diagnostics
- Electrical Wiring Diagram — ROPS Configuration
- Electrical Wiring Diagram — Cabin Configuration
- Engine Starting System — ROPS Configuration
- Engine Starting System — Cabin Configuration
- Cabin Glow Control System
- Operator Presence Control (OPC) System
- Engine Starting Conditions and Automatic Engine Stop
- Battery Charging System
- Lighting System
- Flasher Unit and Brake Light Switch
- Bi-Speed Turn Electrical Circuit
- Bi-Speed Turn System Overview
- Bi-Speed Turn Component Arrangement
- Instrument Panel System
- LCD Monitor Indicator
- Electrical System Troubleshooting
- Electrical Servicing Specifications
- Electrical Tightening Torques
- Battery Inspection and Testing
- Main Switch Testing — ROPS Configuration
- Main Switch Testing — Cabin Configuration
- Bi-Speed Turn Fail-Safe System Inspection
- Bi-Speed Turn Fine-Adjustment
- Bi-Speed Turn Self-Diagnosis
- Bi-Speed Turn Restraint Checking
- Bi-Speed Controller and Main ECU Inspection
- Instrument Panel Diagnostic Checking
- PTO Clutch Control Switch Testing
- Starter Motor and Safety Switch Inspection
- Electrical Relay Testing
- QGS Controller Inspection — Cabin Configuration
- Coolant Temperature Sensor Inspection — Cabin Configuration
- OPC Controller Inspection
- Glow Plug Testing
- Key Stop Solenoid Checking
- Alternator Inspection
- Combination Switch Testing
- Hazard Switch and Beacon Switch Inspection
- Flasher Unit and Headlight Testing
- Brake Light Switch Inspection
- Rear PTO and Mid-PTO Indicator Switches
- Parking Brake and Oil Pressure Indicator Switches
- Electrical Gauge Inspection
- Trailer Socket Inspection
- Starter Motor Disassembly and Assembly
- Alternator Disassembly and Assembly
- Starter Motor Component Servicing
- Alternator Component Servicing
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12. Cabin — Air Conditioning and Servicing
- Cabin Air Conditioning System Overview
- Refrigeration System Construction
- Air Conditioning Compressor
- Compressor Pressure Relief Valve
- Compressor Magnetic Clutch
- Refrigerant Condenser
- Refrigerant Receiver
- Air Conditioner Unit
- Cabin Climate Control System
- Air Conditioning Electrical Circuit
- Air Conditioning Relays
- Cabin Air Conditioning Troubleshooting
- Air Conditioning Servicing Specifications
- Cabin Component Tightening Torques
- Refrigeration System Repair Precautions
- Manifold Gauge and Refrigerant Service Tools
- Refrigerant Recovery and Recycling Equipment
- Refrigerant Pressure Inspection
- Refrigerant System Discharging and Evacuation
- Refrigerant Charging Procedures
- Refrigerant Charge Quantity Checking
- Air Conditioning Compressor Checking
- Air Conditioning Control Panel Inspection
- Blower Switch and A/C Switch Testing
- Mode and Temperature Control Dial Inspection
- Blower Resistor and Blower Motor Testing
- Temperature Control Motor Inspection
- Airflow Mode Motor Inspection
- Air Conditioning Relay and Pressure Switch Testing
- Windshield Wiper Switch Inspection
- Windshield Wiper Motor Inspection
- Cabin Defogger Inspection
- Cabin Separation from Tractor Body
- Air Conditioning Compressor Removal
- Air Conditioner Unit Removal
- Refrigerant Pipe Removal
- Cabin Heater Hose Removal
- Cabin Windshield Removal
- Wiper Motor Disassembly
- Cabin Component Servicing
Bi-Speed Turn Clutch, Hydraulic Controls and Electronic Fail-Safe Diagnosis
The workshop documentation provides three related areas of Bi-Speed Turn coverage. The Transmission chapter explains the hydraulic clutch and gear mechanism, including hydraulic oil flow and power transmission. The Hydraulic System chapter separately documents the Bi-Speed valve and its servicing procedures. The Electrical System chapter adds fail-safe checks, fine-adjustment, self-diagnosis, restraint checking and main ECU testing. When investigating Bi-Speed Turn operation, use these references together to distinguish hydraulic clutch problems from valve-related faults or electronic control issues.
ROPS and cabin configurations also have different equipment separation and electrical servicing procedures. The Engine, Clutch, Rear Axle and Brake chapters identify configuration-specific preparation requirements, while the Electrical System provides separate wiring and starting references. The dedicated Cabin chapter adds refrigeration, climate-control, windshield and wiper servicing. Confirm the machine’s installed configuration before selecting removal instructions, electrical checks or component adjustment procedures.
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