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The Komatsu D20-6 and Its Mechanical Design
The Komatsu D20-6 is a compact crawler dozer developed by Komatsu Ltd., a Japanese manufacturer founded in 1921 and recognized globally for its earthmoving equipment. The D20 series was designed for light-duty grading, land clearing, and agricultural work. With a weight of approximately 8,000 pounds and powered by a Komatsu diesel engine producing around 40 horsepower, the D20-6 featured a mechanical transmission and clutch-based steering system. Its compact size and reliability made it popular among small contractors and landowners.
Unlike hydrostatic machines, the D20-6 uses dry steering clutches and brake bands to control track movement. Each track is independently operated via a clutch and brake combination, allowing the operator to steer by disengaging one track and applying the brake.
Symptoms of Steering Failure
A common issue with the D20-6 is poor or inconsistent steering response. In one case, the machine reversed smoothly on both tracks, but in forward gear, the right steering clutch failed to disengage properly under load. After linkage adjustments, the issue worsened, and grinding noises were observed during operation.
Terminology Explained
In Oklahoma, a landowner restoring a D20-6 encountered a seized left steering clutch. After removing all bolts, he was unable to separate the flanges. Using a chisel between the inner flange and drum, he forced the assembly apart—but narrowly avoided injury when the wedge shot backward. He later opted to cut the outer drum and sourced replacement parts from a regional supplier. The repair restored full steering function, and the machine was used to clear fence lines and grade a driveway.
Preventive Maintenance Tips
Steering clutch issues on the Komatsu D20-6 are often caused by linkage misalignment, water contamination, or mechanical seizure. With careful inspection and methodical disassembly, most problems can be resolved without full transmission removal. Operators should prioritize preventive maintenance and use caution during repairs, as stored energy in clutch assemblies can pose safety risks. The D20-6 remains a capable and serviceable machine when properly maintained.
The Komatsu D20-6 is a compact crawler dozer developed by Komatsu Ltd., a Japanese manufacturer founded in 1921 and recognized globally for its earthmoving equipment. The D20 series was designed for light-duty grading, land clearing, and agricultural work. With a weight of approximately 8,000 pounds and powered by a Komatsu diesel engine producing around 40 horsepower, the D20-6 featured a mechanical transmission and clutch-based steering system. Its compact size and reliability made it popular among small contractors and landowners.
Unlike hydrostatic machines, the D20-6 uses dry steering clutches and brake bands to control track movement. Each track is independently operated via a clutch and brake combination, allowing the operator to steer by disengaging one track and applying the brake.
Symptoms of Steering Failure
A common issue with the D20-6 is poor or inconsistent steering response. In one case, the machine reversed smoothly on both tracks, but in forward gear, the right steering clutch failed to disengage properly under load. After linkage adjustments, the issue worsened, and grinding noises were observed during operation.
Terminology Explained
- Steering Clutch: A friction-based mechanism that disengages power to one track, allowing the dozer to turn.
- Brake Band: A curved friction surface that stops the disengaged track when applied.
- Fork: A mechanical arm that moves the clutch assembly via the steering lever.
- Check for clutch slippage Place the blade against a solid object and engage forward gear. If both tracks rotate evenly, the clutches are likely functioning. Pull each steering lever individually to test disengagement.
- Inspect for water contamination Pull the drain plugs on both clutch housings. Water in the housing can cause rust and clutch failure. Dry clutches should remain clean and dry.
- Evaluate linkage and spool contact The steering valve spool should not be under pressure from the linkage. It must remain in light contact to avoid partial engagement, which can cause clutch drag.
- Disassemble and inspect clutch components If the clutch fails to disengage, remove the cover and attempt to move the fork manually. Stiff movement may indicate seized components or spring tension. Use a pry bar carefully to test fork travel.
- Lubricate fork pivot points Apply penetrating oil to the fork where it passes through the bevel gear flange. Avoid contaminating clutch surfaces.
- Replace worn brake drums or clutch packs If the clutch cannot be freed or the drum is damaged, cutting the outer brake drum may be necessary. Use a small cutting wheel or drill a series of holes to break the drum apart safely.
In Oklahoma, a landowner restoring a D20-6 encountered a seized left steering clutch. After removing all bolts, he was unable to separate the flanges. Using a chisel between the inner flange and drum, he forced the assembly apart—but narrowly avoided injury when the wedge shot backward. He later opted to cut the outer drum and sourced replacement parts from a regional supplier. The repair restored full steering function, and the machine was used to clear fence lines and grade a driveway.
Preventive Maintenance Tips
- Drain clutch housings annually to check for moisture
- Adjust steering linkage every 250 hours
- Lubricate fork pivots and linkage joints quarterly
- Replace brake bands and clutch discs every 2,000 hours or as needed
Steering clutch issues on the Komatsu D20-6 are often caused by linkage misalignment, water contamination, or mechanical seizure. With careful inspection and methodical disassembly, most problems can be resolved without full transmission removal. Operators should prioritize preventive maintenance and use caution during repairs, as stored energy in clutch assemblies can pose safety risks. The D20-6 remains a capable and serviceable machine when properly maintained.
