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The Austin-Western Legacy in Road Grading
Austin-Western was one of the earliest American manufacturers of motor graders, dating back to the early 20th century. Known for their rugged construction and mechanical simplicity, Austin-Western graders were widely used by municipalities and contractors throughout the mid-century. The Super 300 model, produced in the 1960s and 1970s, was a hydraulically operated grader with a reputation for durability and straightforward serviceability. Though the company was eventually absorbed into the Clark Equipment lineage, many Super 300 units remain in service today, especially in rural and private road maintenance.
The Super 300 featured full hydraulic steering, a mechanical circle lock, and a robust frame designed for gravel road shaping and light construction grading. However, as these machines age, certain systems—especially steering and blade rotation—require careful attention and creative solutions.
Diagnosing Jerky Hydraulic Steering
One of the most common complaints with the Super 300 is stiff or “jerky” steering. Unlike modern orbitrol systems, the Super 300 uses a hydraulic ram at the front axle and a fluid-diversion valve mounted at the base of the steering column. This valve, often misunderstood, is responsible for directing hydraulic flow based on steering wheel input.
Terminology note:
Recommended steps:
Circle Lock Failure Under Load
The circle lock mechanism on the Super 300 is designed to hold the blade’s rotational position during grading. It engages via a latch that drops into a toothed ring, preventing unwanted rotation. On some units, this latch is released by a solenoid, which may be activated by a switch on the control lever or a foot pedal.
When the lock fails to stay engaged—especially under torque at the blade toe—it can cause the circle to rotate unexpectedly, ruining grade and risking damage.
Common causes include:
Solutions:
Contrary to some assumptions, the solenoid in the Super 300 does not hold the latch down—it releases it. Gravity and friction are responsible for keeping the latch engaged. If the latch teeth are tapered or the ring is over-lubricated, torque from the blade can force the latch upward, disengaging the lock.
Testing the solenoid:
A Story from the Grader Shed
In Oregon, a retired road builder inherited a Super 300 from a county auction. After restoring the engine and hydraulics, he noticed the blade would rotate during heavy ditching. After inspecting the circle lock, he found the latch teeth had worn into a shallow taper. He ground them flat, cleaned the ring, and added a spring-loaded detent to hold the latch. The grader held its position even under full blade torque, and he went on to regrade three miles of gravel road without issue.
Preserving and Operating Vintage Graders
Operating a Super 300 requires a blend of mechanical intuition and historical knowledge. Unlike joystick-controlled modern graders, the Super 300 demands deliberate hand coordination and awareness of hydraulic feedback. Steering is not continuous—it’s flicked, nudged, and modulated with feel.
Tips for longevity:
The Austin-Western Super 300 remains a testament to mid-century engineering—simple, powerful, and repairable. While parts may be scarce, solutions are often found in the ingenuity of operators and the wisdom of mechanics who’ve kept these machines alive for decades. Whether grading vineyard rows or shaping rural roads, the Super 300 still earns its place in the shed, one hydraulic flick at a time.
Austin-Western was one of the earliest American manufacturers of motor graders, dating back to the early 20th century. Known for their rugged construction and mechanical simplicity, Austin-Western graders were widely used by municipalities and contractors throughout the mid-century. The Super 300 model, produced in the 1960s and 1970s, was a hydraulically operated grader with a reputation for durability and straightforward serviceability. Though the company was eventually absorbed into the Clark Equipment lineage, many Super 300 units remain in service today, especially in rural and private road maintenance.
The Super 300 featured full hydraulic steering, a mechanical circle lock, and a robust frame designed for gravel road shaping and light construction grading. However, as these machines age, certain systems—especially steering and blade rotation—require careful attention and creative solutions.
Diagnosing Jerky Hydraulic Steering
One of the most common complaints with the Super 300 is stiff or “jerky” steering. Unlike modern orbitrol systems, the Super 300 uses a hydraulic ram at the front axle and a fluid-diversion valve mounted at the base of the steering column. This valve, often misunderstood, is responsible for directing hydraulic flow based on steering wheel input.
Terminology note:
- Fluid-Diversion Valve: A hydraulic control unit that modulates flow to the steering ram based on wheel rotation.
- Orbitrol: A modern hydraulic steering control unit that provides smooth, proportional response.
Recommended steps:
- Flush the hydraulic system and replace fluid with ISO 46-grade oil.
- Remove and inspect the valve for scoring, debris, or hardened seals.
- Rebuild kits may be difficult to source, but custom seal matching is possible through hydraulic shops.
- Check for air in the system, which can cause erratic steering response.
Circle Lock Failure Under Load
The circle lock mechanism on the Super 300 is designed to hold the blade’s rotational position during grading. It engages via a latch that drops into a toothed ring, preventing unwanted rotation. On some units, this latch is released by a solenoid, which may be activated by a switch on the control lever or a foot pedal.
When the lock fails to stay engaged—especially under torque at the blade toe—it can cause the circle to rotate unexpectedly, ruining grade and risking damage.
Common causes include:
- Worn or tapered latch teeth that allow the lock to slip under load.
- Excessive grease on the circle ring, reducing friction and allowing movement.
- Weak solenoid that cannot fully retract or hold the latch.
- Missing or bypassed mechanical retention systems.
Solutions:
- Grind the latch teeth flat to increase surface contact and reduce slip.
- Reduce grease on the circle ring to allow better mechanical engagement.
- Replace or reinforce the solenoid with a higher-torque unit.
- Add a mechanical spring or detent to hold the latch in place once engaged.
Contrary to some assumptions, the solenoid in the Super 300 does not hold the latch down—it releases it. Gravity and friction are responsible for keeping the latch engaged. If the latch teeth are tapered or the ring is over-lubricated, torque from the blade can force the latch upward, disengaging the lock.
Testing the solenoid:
- Bench test with 12V power to confirm pull strength.
- Measure resistance and current draw to ensure proper function.
- Inspect wiring and switch placement for corrosion or misalignment.
A Story from the Grader Shed
In Oregon, a retired road builder inherited a Super 300 from a county auction. After restoring the engine and hydraulics, he noticed the blade would rotate during heavy ditching. After inspecting the circle lock, he found the latch teeth had worn into a shallow taper. He ground them flat, cleaned the ring, and added a spring-loaded detent to hold the latch. The grader held its position even under full blade torque, and he went on to regrade three miles of gravel road without issue.
Preserving and Operating Vintage Graders
Operating a Super 300 requires a blend of mechanical intuition and historical knowledge. Unlike joystick-controlled modern graders, the Super 300 demands deliberate hand coordination and awareness of hydraulic feedback. Steering is not continuous—it’s flicked, nudged, and modulated with feel.
Tips for longevity:
- Keep hydraulic fluid clean and inspect filters regularly.
- Use manual override systems only when solenoids fail.
- Maintain blade teeth and circle ring engagement surfaces.
- Store the machine under cover to protect electrical components.
The Austin-Western Super 300 remains a testament to mid-century engineering—simple, powerful, and repairable. While parts may be scarce, solutions are often found in the ingenuity of operators and the wisdom of mechanics who’ve kept these machines alive for decades. Whether grading vineyard rows or shaping rural roads, the Super 300 still earns its place in the shed, one hydraulic flick at a time.
