09-26-2025, 12:52 PM
Mitsubishi’s Entry into the Grader Market
Mitsubishi Heavy Industries, a cornerstone of Japan’s industrial development since the late 19th century, expanded into construction machinery in the post-war era. While better known for engines, ships, and aerospace systems, Mitsubishi also produced a line of motor graders aimed at infrastructure development across Asia and the Middle East. The MG400 was one of its flagship models, designed for mid-size grading tasks such as road leveling, ditch shaping, and site preparation. Though not as globally dominant as Caterpillar or Komatsu, Mitsubishi graders earned a reputation for mechanical simplicity and rugged steel construction.
MG400 Specifications and Operating Profile
The Mitsubishi MG400 is a conventional articulated motor grader with a rear-mounted engine and six-wheel drive. Its key dimensions include:
Terminology Notes
Operators of the MG400 often report issues related to hydraulic responsiveness and wear in the circle drive assembly. Over time, the moldboard may drift under load due to internal leakage in control valves or worn seals in the hydraulic cylinders. The circle drive, which rotates the blade, can suffer from gear backlash or uneven wear, leading to grading inaccuracies.
In one case, a road crew in Pakistan found that the MG400’s blade would rotate unintentionally during heavy grading. Upon inspection, the circle drive gear teeth were rounded off due to lack of lubrication. The team fabricated replacement gears locally and installed a grease port to prevent recurrence.
Electrical System and Parts Availability
The MG400’s electrical system is basic, relying on analog gauges and mechanical switches. While this simplicity aids field repairs, it also means that wiring harnesses and connectors are prone to corrosion and fatigue. Replacement parts for the MG400 can be difficult to source outside of Japan, especially for proprietary hydraulic fittings and engine components.
Operators often resort to:
Blade Control and Operator Ergonomics
The MG400 features dual joystick or lever controls for blade lift, tilt, and rotation. While functional, the ergonomics lag behind modern graders with fingertip electrohydraulic controls. Long shifts can lead to operator fatigue, especially when fine grading is required. Some owners have upgraded seats and added vibration-dampening mats to improve comfort.
Field Anecdote and Improvisation
In 2015, a municipal crew in Sri Lanka used an MG400 to grade a flood-damaged road. The moldboard hydraulic cylinder failed mid-operation, and no replacement was available. The crew repurposed a cylinder from a farm tractor, adapting the mounting brackets and hydraulic lines. The grader completed the job and remained in service for another year before a proper rebuild was performed.
Recommendations for Long-Term Operation
The MG400 was never mass-produced at the scale of Caterpillar’s 140 series or Komatsu’s GD graders, but it filled a niche in developing regions where simplicity and durability were valued over advanced electronics. Mitsubishi eventually phased out grader production to focus on engines and power systems, leaving the MG400 as a legacy machine still operating in remote areas.
Conclusion
The Mitsubishi MG400 motor grader is a testament to mechanical resilience and field adaptability. While parts scarcity and aging hydraulics pose challenges, its straightforward design allows for creative repairs and continued service. For operators willing to invest in maintenance and improvisation, the MG400 remains a capable tool for roadwork and site grading in environments where newer machines may be impractical or cost-prohibitive.
Mitsubishi Heavy Industries, a cornerstone of Japan’s industrial development since the late 19th century, expanded into construction machinery in the post-war era. While better known for engines, ships, and aerospace systems, Mitsubishi also produced a line of motor graders aimed at infrastructure development across Asia and the Middle East. The MG400 was one of its flagship models, designed for mid-size grading tasks such as road leveling, ditch shaping, and site preparation. Though not as globally dominant as Caterpillar or Komatsu, Mitsubishi graders earned a reputation for mechanical simplicity and rugged steel construction.
MG400 Specifications and Operating Profile
The Mitsubishi MG400 is a conventional articulated motor grader with a rear-mounted engine and six-wheel drive. Its key dimensions include:
- Operating length: approximately 28 feet 1 inch
- Width: around 7 feet 9 inches
- Height: roughly 11 feet 1 inch
- Operating weight: close to 31,440 pounds
Terminology Notes
- Moldboard: The curved blade used to cut, spread, and level material.
- Articulation Joint: A pivot point in the frame that allows the front and rear halves of the grader to bend, improving maneuverability.
- Circle Drive: The gear mechanism that rotates the moldboard horizontally.
- Scarifier: A row of teeth mounted ahead of the moldboard used to break up compacted surfaces.
Operators of the MG400 often report issues related to hydraulic responsiveness and wear in the circle drive assembly. Over time, the moldboard may drift under load due to internal leakage in control valves or worn seals in the hydraulic cylinders. The circle drive, which rotates the blade, can suffer from gear backlash or uneven wear, leading to grading inaccuracies.
In one case, a road crew in Pakistan found that the MG400’s blade would rotate unintentionally during heavy grading. Upon inspection, the circle drive gear teeth were rounded off due to lack of lubrication. The team fabricated replacement gears locally and installed a grease port to prevent recurrence.
Electrical System and Parts Availability
The MG400’s electrical system is basic, relying on analog gauges and mechanical switches. While this simplicity aids field repairs, it also means that wiring harnesses and connectors are prone to corrosion and fatigue. Replacement parts for the MG400 can be difficult to source outside of Japan, especially for proprietary hydraulic fittings and engine components.
Operators often resort to:
- Rewiring harnesses using marine-grade cable
- Retrofitting hydraulic lines with universal fittings
- Replacing gauges with aftermarket equivalents
Blade Control and Operator Ergonomics
The MG400 features dual joystick or lever controls for blade lift, tilt, and rotation. While functional, the ergonomics lag behind modern graders with fingertip electrohydraulic controls. Long shifts can lead to operator fatigue, especially when fine grading is required. Some owners have upgraded seats and added vibration-dampening mats to improve comfort.
Field Anecdote and Improvisation
In 2015, a municipal crew in Sri Lanka used an MG400 to grade a flood-damaged road. The moldboard hydraulic cylinder failed mid-operation, and no replacement was available. The crew repurposed a cylinder from a farm tractor, adapting the mounting brackets and hydraulic lines. The grader completed the job and remained in service for another year before a proper rebuild was performed.
Recommendations for Long-Term Operation
- Inspect circle drive gears every 500 hours and lubricate regularly
- Replace hydraulic seals and hoses every 1,000 hours or sooner in hot climates
- Upgrade electrical connectors to weatherproof standards
- Keep a log of blade drift and hydraulic responsiveness to anticipate failures
- Source parts from regional Mitsubishi industrial suppliers or fabricate locally when possible
The MG400 was never mass-produced at the scale of Caterpillar’s 140 series or Komatsu’s GD graders, but it filled a niche in developing regions where simplicity and durability were valued over advanced electronics. Mitsubishi eventually phased out grader production to focus on engines and power systems, leaving the MG400 as a legacy machine still operating in remote areas.
Conclusion
The Mitsubishi MG400 motor grader is a testament to mechanical resilience and field adaptability. While parts scarcity and aging hydraulics pose challenges, its straightforward design allows for creative repairs and continued service. For operators willing to invest in maintenance and improvisation, the MG400 remains a capable tool for roadwork and site grading in environments where newer machines may be impractical or cost-prohibitive.
