Both the STα-30 and STα-35 get factory-level service coverage here, from the HST drivetrain and Bi-Speed Turn hydraulic clutch pack to the steering and electrical systems. Hydraulic schematics trace fluid through the position control, flow priority, relief, and auxiliary valves, while 14 pages of troubleshooting sit alongside wiring diagrams for the starting, charging, and lighting circuits. Exploded views break down every major assembly: engine internals, clutch, all four transmission sections, front and rear axles, and brakes. Fill the crankcase to 4.5 L after a filter change, top the fuel tank to 29.5 L, and book the first engine oil change at 50 hours, then every 200 after that. No more hunting spec sheets across three sources. Pull it up on a tablet, search by keyword, and fix the machine.
What's Inside This Kubota STα-30, STα-35 Manual
| System | Pages | Key Topics |
|---|---|---|
| G General | 13-57 | General |
| 1 Engine | 58-116 | Fuel System, Cylinder Head and Valves, Piston and Connecting Rod, Crankshaft, Lubricating System, Cooling System |
| 2 Clutch | 117-135 | Clutch Disc, Pressure Plate, Diaphragm Spring, Release Bearing, Clutch Shaft, Clutch Release Fork |
| 3 Transmission | 136-191 | Hydrostatic Transmission (HST), Range Gear Shift Section, Front Wheel Drive Shift Section, Rear PTO Shift Section, Mid-PTO Shift Section, Differential Gear |
| 4 Rear Axle | 192-200 | Rear Axle Case, Planetary Gear, Differential Lock Fork, Hypoid Ring Gear, Rear Axle Shaft, Planetary Carrier |
| 5 Brakes | 201-210 | Brake Pedal, Brake Disc, Cam Plate, Brake Shaft, Parking Brake Lever |
| 6 Front Axle | 211-230 | Front Wheel Alignment, Front Axle Case, Bevel Gear Case, Differential Gear, Pinion Shaft, Front Axle Bracket |
| 7 Bi-Speed Turn | 231-254 | Hydraulic Clutch Pack, Bi-speed Solenoid Valve, Front Wheel Turning Angle Sensor, Travelling Speed Sensor, Controller Unit, Bi-speed Switch |
| 8 Steering | 255-276 | Hydraulic Pump, Steering Controller, Steering Cylinder, Power Steering Hoses, Tie-rod End |
| 9 Hydraulic System | 277-312 | Hydraulic Pump, Position Control Valve, Flow Priority Valve, Relief Valve, Hydraulic Cylinder, Auxiliary Control Valve |
| 10 Electrical System | 313-359 | Wiring Diagram, Starting System, Charging System, Lighting System, Gauges |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| General Use Screws, Bolts and Nuts (M6, No-grade or 4T) | 7.85 to 9.31 N·m | p. 23 |
| General Use Screws, Bolts and Nuts (M8, No-grade or 4T) | 17.7 to 20.5 N·m | p. 23 |
| Fuel tank capacity | 29.5 L (7.79 U.S.gals., 6.49 Imp.gals.) | p. 22 |
| Engine crankcase (with filter) capacity | 4.5 L (1.19 U.S.gals., 0.99 Imp.gals.) | p. 22 |
| Engine oil change | Initial 50 hours, Every 200 hours | p. 24 |
| Engine oil filter replace | Initial 50 hours, Every 200 hours | p. 24 |
| Engine Oil Capacity (with filter) | 4.5 L | p. 9 |
| Engine Coolant Capacity (with recovery tank) | 5.8 L | p. 9 |
| Transmission Fluid Capacity | 18.5 L | p. 9 |
| Front Axle Case Oil Capacity | 4.0 L | p. 9 |
| General Use Screws, Bolts and Nuts Tightening Torque (M10, Ordinariness) | 39.3 to 45.1 N·m | p. 23 |
| Clutch Pedal Free Travel | 20.0 to 30.0 mm | p. 28 |
Kubota STα-30, STα-35 Common Problems This Manual Covers
Engine overheats under heavy load on the STα-30 or STα-35, with coolant pushing out of the overflow
Inspect the cooling system components. Check the fan belt tension, which must sit between 7 to 9 mm as shown on page 33. Test the radiator cap pressure falling time on page 71, and replace the cap if it falls below 10 seconds.
Manual Section: 1 EngineTractor hesitates between gears, or the transmission slips under heavy PTO load during field work p. 117
Measure the clutch pedal free travel and adjust the linkage to 20.0 to 30.0 mm, per page 28. If the clutch keeps dragging, check the pressure plate and clutch disc for wear or glazing.
Manual Section: 2 ClutchEngine cranks slowly and puffs white smoke from the exhaust, with no start in cold weather
Test the engine compression against the factory spec of 3.53 to 4.02 MPa on page 66. If it reads low, pull the cylinder head cover and check valve clearances (0.18 to 0.22 mm cold) before you inspect the piston rings.
Manual Section: 1 EngineBattery drains fast during operation and the charging indicator lamp stays lit on the dash panel p. 313
Trace the charging system wiring with the diagram on page 316. Confirm the alternator belt is tight, then torque the alternator pulley nut to 58.3 to 78.9 N·m as specified on page 336. If the battery fails a load test, replace it.
Manual Section: 10 Electrical SystemFrequently Asked Questions
What are the recommended service intervals?
A full service-interval table runs through the manual. The first checks and changes land at 50 hours, including engine oil and the hydraulic oil filter. Fan belt and brake adjustments then come every 100 hours, while transmission fluid and front axle case oil changes fall every 400 hours. Flush the cooling system and change the coolant every 2 years.
What fluids and capacities does this machine require?
The 29.5 L (7.79 U.S.gals.) tank takes No. 2-D diesel fuel. The engine crankcase holds 4.5 L (1.19 U.S.gals.) of API service CC or CD class oil, and the cooling system takes 5.8 L (1.56 U.S.gals.) of fresh clean water with anti-freeze. The transmission case holds 18.5 L (4.89 U.S.gals.) of KUBOTA SUPER UDT fluid, while the front axle case holds 4.0 L (1.06 U.S.gals.) of KUBOTA SUPER UDT fluid or SAE80, 90 gear oil.
How to troubleshoot engine won't start?
When the engine won't fire, start with the basics: no fuel (replenish, page G-8), air in the fuel system (bleed, page G-28), or a clogged fuel filter (change, page G-18). Less obvious culprits are incorrect injection timing (adjust, page 1-S50) and a compression leak from the cylinder (replace the head gasket, page 1-S20).
What are the hydraulic system specifications?
At 2800 rpm and a rated pressure of 16.67 to 16.72 MPa (170.0 to 170.5 kgf/cm2), the hydraulic pump delivers 19.9 L/min. Relief valve setting pressure runs 10.7 to 11.7 MPa (109 to 119 kgf/cm2). The cylinder bore I.D. spec is 75.06 to 75.10 mm, with a 75.20 mm allowable limit.
How quickly can I access this Kubota STα-30, STα-35 manual after buying?
A 359-page Workshop Manual in searchable PDF format, ready the moment checkout completes. View it on a computer, tablet, or phone. No shipping wait.
Are there any print restrictions on this Kubota STα-30, STα-35 manual?
Absolutely. No DRM or copy protection. Print the whole manual or just the pages you need. Any home or office printer works.
Are there wiring harness diagrams in this Kubota STα-30, STα-35 manual?
Included. The Kubota STα-30, STα-35 Workshop Manual covers complete wiring harness diagrams, electrical circuits, and connector pinouts.
Document Quality
This document is a native digital PDF, ensuring that you can easily search and copy all text content. The text is consistently crisp and highly readable on every page, with no blurriness or fading. Diagrams and illustrations are sharp, appearing to be vector-based, which means all lines and labels remain perfectly clear even at high zoom levels. The pages are clean and free from any scan artifacts, stains, or skewed elements. You will find several intentionally blank pages that serve as clear chapter dividers.
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