Troubleshooting Final Drive Issues on the Bobcat 864

[MikePhua]

The Bobcat 864 and Its Hydraulic Drive System
The Bobcat 864 was introduced in the late 1990s as a compact track loader designed for demanding terrain and heavy-duty applications. With a 73-horsepower turbocharged diesel engine and a rated operating capacity of over 2,000 pounds, the 864 quickly became a favorite among contractors, landscapers, and demolition crews. Its rubber track system and hydraulic final drives gave it superior traction and maneuverability compared to wheeled skid steers.
Bobcat, founded in 1947, had already established itself as a leader in compact equipment. The 864 was part of a transitional generation that blended mechanical simplicity with hydraulic sophistication. Its final drive motors—located at each track—are responsible for converting hydraulic pressure into rotational torque, propelling the machine forward and backward.
Terminology Notes

• Final Drive Motor: A hydraulic motor that powers the track system, converting fluid pressure into mechanical rotation.
  
• Case Drain Line: A low-pressure return line that carries leakage oil from the motor housing back to the reservoir.
  
• Planetary Gearbox: A gear system that multiplies torque and reduces speed, located between the motor and the track sprocket.
  
• Charge Pressure: The baseline hydraulic pressure required to keep the motor primed and prevent cavitation.
  

Symptoms of Final Drive Failure
Operators may observe:

• One track moves slower or not at all
  
• Audible whining or grinding from the drive motor
  
• Hydraulic fluid leaking near the sprocket or motor housing
  
• Machine veers to one side during travel
  
• Loss of torque under load or incline
  

In one case, a contractor in Alberta noticed his Bobcat 864 pulling hard to the left. After inspecting the final drive, he found the right-side motor had a failed seal, causing internal leakage and reduced pressure.
Root Causes and Diagnostic Pathways
Final drive issues can stem from hydraulic, mechanical, or electrical faults. Key areas to inspect include:

• Case Drain Pressure
  • Excessive backpressure can damage motor seals and bearings
    
  • Solution: Test case drain pressure (should be under 30 psi) and replace clogged filters
    
• Motor Seal Failure
  • Internal leakage reduces torque and causes overheating
    
  • Solution: Rebuild motor with OEM seal kit and inspect shaft for scoring
    
• Planetary Gear Wear
  • Worn gears or bearings cause noise and reduced efficiency
    
  • Solution: Disassemble gearbox, inspect gear teeth, and replace worn components
    
• Hydraulic Contamination
  • Dirt or water in fluid accelerates wear and causes valve sticking
    
  • Solution: Flush system, replace fluid and filters, and test for water content
    
• Electrical Control Faults
  

• If equipped with electronic drive control, sensor failure may affect motor response
  
• Solution: Scan for fault codes and test voltage at motor solenoids
  

A technician in Texas resolved a sluggish drive issue by replacing the case drain filter and resealing the motor. The machine regained full travel speed and passed a 10-hour grading test without recurrence.
Preventive Maintenance and Upgrade Options
To extend final drive life:

• Replace hydraulic filters every 500 hours
  
• Inspect case drain flow and pressure quarterly
  
• Monitor fluid temperature and contamination levels
  
• Use synthetic hydraulic fluid with anti-wear additives
  
• Clean motor housing and sprocket area monthly
  

Some owners retrofit their Bobcat 864s with external case drain pressure gauges and magnetic drain plugs. A crew in Argentina added a digital flow meter to monitor motor performance in real time, reducing downtime and improving diagnostics.
Operator Anecdotes and Field Wisdom
A retired operator in Montana recalled his 864 losing drive during a winter job. After checking the basics, he discovered ice buildup around the case drain line, causing backpressure and seal failure. Thawing and rerouting the line solved the issue.
In British Columbia, a demolition team trained operators to recognize early signs of final drive wear—such as increased fuel consumption or uneven track speed. This proactive approach reduced motor replacements and extended service intervals by 25%.
Recommendations for Technicians and Fleet Managers
When servicing final drives:

• Use hydraulic schematics to trace case drain and supply circuits
  
• Document pressure readings and motor rebuild intervals
  
• Train operators on proper warm-up and travel technique
  
• Stock spare seals, filters, and gear components
  
• Coordinate with Bobcat support for updated service bulletins
  

A fleet manager in Georgia created a final drive inspection checklist including case drain pressure test, gear wear log, and fluid analysis. This improved uptime and reduced travel-related faults across his compact loader fleet.
Conclusion
Final drive problems on the Bobcat 864 are often rooted in hydraulic restriction, seal failure, or gear wear. With precise diagnostics, preventive care, and thoughtful upgrades, technicians can restore full travel performance and protect critical components. In track loaders, mobility is power—and the final drive must deliver it reliably, every time.