Servicing the Track Drive Gearbox on the 2004 Case CX25 Mini Excavator

[MikePhua]

The Case CX25 and Its Kobelco Lineage
The Case CX25 mini excavator, introduced in the early 2000s, was part of Case Construction’s compact equipment lineup aimed at utility contractors, landscapers, and municipal crews. With an operating weight of approximately 5,500 lbs and a digging depth of over 8 feet, the CX25 offered a balance of maneuverability and hydraulic power. Notably, this model was a rebadged version of the Kobelco SK25SR-2, sharing components and design features, including its track drive system.
The track drive gearbox on the CX25 is manufactured by Kayaba Industry, a Japanese hydraulic specialist known for producing final drives and swing motors for compact equipment. The specific unit used is the Kayaba MAG-18VP-200E, a compact planetary drive motor with integrated reduction gearing and floating seals.
Terminology Annotation
- Final Drive: The last stage of power transmission from the hydraulic motor to the tracks, typically involving planetary gears and a sealed housing.
- Floating Seal: A mechanical face seal consisting of two metal rings and elastomeric O-rings, used to prevent oil leakage and contamination in rotating assemblies.
- Face Plate Cover: The outer housing of the drive motor that must be removed to access internal seals and bearings.
- Leader Wire: A steel wire used to assist in the removal of internal retaining components during disassembly.
Disassembly Challenges and Techniques
Servicing the track drive gearbox requires careful handling of the face plate cover and internal wire retainer. The cover is held in place by a wire accessed through a small plug hole. Removing this wire without damaging it is critical, as it secures the internal components and allows the cover to be withdrawn.
Recommended steps:
• Remove the plug and use needle-nose pliers or a hook to extract the wire
• Thread bolts into the cover’s tapped holes and use a bar to gently rotate the cover while pulling on the wire
• If rotation fails, insert a long bolt into the center fill hole to press against the internal shaft and gradually push the cover outward
• Avoid using undersized bolts or excessive force, which may damage threads or internal gear components
This method was successfully used by a retired highway technician who demonstrated that controlled pressure through the center hole could release the cover without binding or distortion.
Seal Identification and Replacement
The floating seal inside the MAG-18VP-200E is a unique size, supplied exclusively to Case and Kobelco. The OEM part number is PM15V01004S002. If the steel rings show no wear, only the O-rings may need replacement. These can be matched at industrial supply houses using calipers and durometer testing.
Steps for seal replacement:
• Clean all mating surfaces thoroughly
• Inspect steel rings for scoring or pitting
• Replace O-rings with matched elastomeric seals rated for hydraulic oil
• Reassemble with care to avoid pinching or misalignment
• Torque bolts to spec and test for leaks under pressure
Hydraulic Line Access and Removal
One common obstacle is the small hydraulic line mounted at a 90-degree angle on the motor body. This line may block access to mounting bolts and resist removal due to limited space. If the fitting cannot be loosened, options include:
• Cutting the hose and replacing it with a matched hydraulic line
• Tracing the hose through the protective sleeve to its termination point on the lower right side of the machine
• Using a crowfoot wrench or custom tool to access the bushing without removing the motor
Always depressurize the hydraulic system before disconnecting lines and cap open ports to prevent contamination.
Recommendations for Maintenance and Documentation
To ensure long-term reliability:
• Keep a printed copy of the drive unit repair manual or request digital sections from authorized dealers
• Label hydraulic lines and fittings during disassembly for accurate reinstallation
• Use metric bolts and tools to avoid thread damage
• Replace seals and gaskets with OEM or high-quality aftermarket parts
• Maintain a service log with part numbers and torque specs for future reference
For operators without access to a full manual, contacting Kobelco support or regional Case dealers may yield technical documentation specific to the MAG-18VP-200E unit.
Conclusion
Servicing the track drive gearbox on the Case CX25 mini excavator requires precision, patience, and familiarity with the Kayaba MAG-18VP-200E drive motor. With the right tools and techniques, even stubborn components like the face plate cover and floating seals can be addressed without damage. Understanding the shared lineage with Kobelco machines opens up additional support channels and parts sourcing options. For compact excavator owners committed to maintaining their machines, mastering final drive service is a valuable skill that pays dividends in uptime and performance.