A DX300 Swing Reduction Gearbox that has covered high hours will usually show it through noise on swing, oil weeping past the seals and a drop in swing torque and swing speed. Replacing the whole assembly is faster and more predictable than replacing gears one by one. RITO supplies the complete DX300 Swing Reduction Gearbox for standard excavators, tested for backlash and preload before packing.
Item NO.:
DX300Order(MOQ):
1pcsPayment:
T/T, WESTERN UNION, CHINESE BANK,PAYPALProduct Origin:
JAPANShipping Port:
Huangpu,GuangzhouLead Time：
In StockRITO supplies the DX300 Swing Reduction Gearbox as a factory-assembled reduction unit for the swing drive of standard excavators. Because the ring gear, planets and bearings are matched as a set, the assembly avoids the noise and heat that follow a partial rebuild, and the pre-set bearing preload removes the need for field shimming. Mounting holes, output spline and overall envelope follow the original dimensions so existing guards and hoses still fit.
| Part Number | DX300 |
| Part Name | Swing Reduction Gearbox |
| Compatible Brand | Doosan |
| Applicable Models | DX300 |
| Application | Excavator swing reduction unit in the upper structure swing circuit |
| Material | Cast iron housing with hardened alloy steel gear set |
| Product Color | Industrial grey / OEM color |
| Working Temperature | -25°C~+80°C |
| Key Function | Turns motor torque into controlled swing rotation |
| Condition | 100% New |
| Packaging | Wooden Case Reinforced Carton Neutral Packing Customized Box |
 | Complete Assembly Ring gear, planets, carriers, bearings, seals and output shaft arrive as one unit, so nothing is reused from a worn original. |
 | Matched Gear Set Ring gear and planet gears are lapped as a matched set, so tooth contact is full width from the first hour and the unit stays quiet under load. |
 | Factory Preload Bearings are shimmed and preloaded on the assembly line, which removes the end float that causes noise and premature wear in field rebuilds. |
 | Double-Lip Sealing A double-lip output seal plus O-ring joints keep abrasive dust out of the oil, the main reason reduction units fail early on demolition and quarry work. |
Q: Do I need to adjust backlash after fitting?
A: No. Backlash and bearing preload are set at assembly. Fit the unit, fill with the specified oil grade, and check for leaks after the first few hours of operation.
Q: Is this a complete assembly or just the gear set?
A: It is supplied as a complete reduction assembly - housing, ring gear, planet gears, carriers, bearings, seals and output shaft - so nothing has to be transferred from the old unit.
Q: How do I confirm this DX300 unit fits my machine?
A: Compare the mounting bolt pattern, the output spline and the overall height against the unit on your machine, and check the model plate. If the numbers differ, send us a photo of the plate and we will confirm the correct variant.
Q: What usually causes these reduction units to fail?
A: Contaminated oil and lost bearing preload. Once dust enters through a worn seal, the bearings loosen, the gear mesh misaligns and the unit starts to whine and overheat within a few hundred hours.
Q: Which oil should I use after installation?
A: Use the grade listed in the machine service manual for the final drive or swing reduction. Overfilling causes heat; underfilling causes immediate bearing damage, so fill to the level plug.
Q: Can this unit be used as an upgrade on an older machine?
A: Where the mounting pattern and spline match, the later specification can be fitted to earlier machines. Confirm the interface dimensions with us before ordering.
Q: Why Choose RITO?
A: Listed Factory
Stable&Reliable Quality
OEM Factory for Chinese Top Excavator Brands
Supplier to Fortune 500 Companies
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