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Why Is the Drive Motor Leaking into the Chain Case
#1
The Eaton/Char-Lynn Motor and Its Role in Skid Steers
The Eaton/Char-Lynn hydraulic drive motor is a widely used component in compact equipment like skid steers. Eaton Corporation, founded in 1911, has evolved into a global leader in power management technologies. Its Char-Lynn division specializes in low-speed, high-torque motors, particularly orbital motors used in mobile machinery. These motors convert hydraulic pressure into rotational motion, driving the wheels or tracks of skid steers with precision and durability. The 6000 series, often found in mid-size machines, is known for its compact design and robust torque output.
Skid steers equipped with Char-Lynn motors typically operate in harsh environments—mud, dust, vibration, and temperature extremes. With over 4200 hours logged on the machine in question, the motor’s internal wear is not unexpected. Regular hydraulic filter changes and maintenance help, but they cannot fully prevent the gradual degradation of internal components.
Symptoms and Early Warning Signs
A common failure mode for these motors is internal leakage into the chain case. This occurs when hydraulic fluid bypasses internal seals and flows into the mechanical housing. Operators may notice:
  • Increased oil levels in the chain case
  • Reduced hydraulic performance
  • Dust accumulation on the motor housing due to oil weeping
  • Shaft seal blowouts caused by pressure imbalance
In one case, a technician noticed a thick coat of dust on a previously replaced motor—an indicator of minor leakage. Though not dripping, even a few drops of oil can attract dust and signal deeper issues.
Why Rebuilding Often Fails
Rebuilding Char-Lynn motors is notoriously difficult. The internal valve plate, a critical component that regulates fluid flow, is prone to scratching. These scratches allow oil to bleed into unintended areas, compromising seal integrity. While some workshops offer valve plate resurfacing using a lapping table—a precision grinding surface—success is rare unless the damage is minimal.
Experienced mechanics report that attempts to rebuild often end in disappointment. The tolerances inside these motors are tight, and once wear exceeds a certain threshold, replacement becomes the only viable option. One technician swore off rebuilding after three failed attempts, citing poor results and wasted labor.
Cost Considerations and Market Pricing
Replacement costs vary widely. A dealer quoted $2872.75 for a new motor, while online sources listed similar units for $1459.00 USD. Inspection services may charge around $260.00 to disassemble and evaluate the motor, with the fee credited toward a replacement if needed. This pricing disparity reflects markup, regional availability, and OEM branding.
To determine compatibility, technicians must locate the motor’s part number. In one case, the tag read 112-1160-006, likely identifying it as a standard 6000 series motor. However, additional codes like 33806 and 1547 C may indicate custom configurations or production batches.
Access Challenges and Maintenance Frustrations
Skid steer design complicates motor access. Operators often struggle to locate tags due to obstructing hoses and tight compartments. Belly pans may resist removal due to seized bolts, and hydraulic suction hoses can weep slightly, adding to the confusion. These frustrations are common in field maintenance, where time and access are limited.
One operator lamented the constant need for repairs, echoing a sentiment shared across the industry. Compact equipment is indispensable but demands vigilance and patience.
Recommendations for Operators
To manage drive motor issues effectively, consider the following:
  • Monitor chain case oil levels regularly
  • Inspect motor housings for dust accumulation or wet spots
  • Avoid rebuilding unless damage is minimal and verified
  • Compare OEM and aftermarket pricing before purchasing
  • Use part numbers to confirm compatibility
  • Tighten hose clamps and inspect suction lines for weeping
  • Apply anti-seize compound to belly pan bolts during reassembly
A Broader Perspective on Hydraulic Motor Failures
Hydraulic motor failures are not unique to skid steers. In 2021, a fleet of forestry harvesters in British Columbia experienced similar issues due to contaminated hydraulic fluid. The motors failed prematurely, prompting a recall and redesign of the filtration system. This incident highlights the importance of fluid cleanliness and proactive maintenance.
Final Thoughts
Drive motor leakage into the chain case is a symptom of deeper wear, often beyond the reach of seal kits or quick fixes. While Eaton/Char-Lynn motors are engineered for durability, they are not immune to time and usage. Operators must weigh the cost of replacement against downtime and repair uncertainty. In most cases, replacing the motor with a verified compatible unit is the most reliable path forward.
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