Doosan DH220-5 Travel Gear Box 170402-00028 Excavator Gearbox

Doosan Excavator DH220-5 Travel Reduction Gearbox 170402-00028 Replacement Part Crawler Excavator

The travel reducer of an excavator (commonly known as the travel gearbox) is a core transmission component connecting the hydraulic motor to the track drive wheel. It functions to reduce rotational speed and increase torque, providing low-speed and high-torque driving force for the tracks.
Core Structure (Three-stage Planetary Gear)
• Sun Gear: Connected to the input of the hydraulic motor and serves as the power source.
• Planet Gears: 3 to 4 pieces, rotate both around the sun gear and on their own axes to transmit power.
• Ring Gear (Internal Gear Ring): Fixed or floating, meshed with the planet gears.
• Planet Carrier: Outputs power to drive the reducer housing and track drive wheel.
• Housing and Bearings: High-strength housing provides dustproof and leakproof performance; heavy-duty bearings support rotational movement.
• Brake: Built-in multi-disc parking brake, hydraulically released and spring-applied, preventing slope rolling.
Working Principle
The hydraulic motor outputs power with high speed and low torque → feeds into the travel reducer → three-stage planetary gears achieve step-by-step speed reduction → outputs power with low speed and high torque → drives the track for traveling.
Common Faults and Causes
1. Abnormal noise / Excessive noise: Gear wear, bearing damage, insufficient lubricant or deteriorated oil quality.
2. Oil leakage: Aging seals, housing cracks, excessive oil level.
3. Weak travel / Track deviation: Gear or bearing wear, brake failure to release, inconsistent performance between left and right reducers.
4. Overheating: Overload, poor lubrication, insufficient heat dissipation, brake dragging.
5. Gear jumping / Sticking: Broken gear teeth, damaged planet carrier, foreign matter ingress.

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