Diagnosing Drive Motor Misalignment and Frame Damage on the Bobcat 864 Track Loader

[MikePhua]

The Bobcat 864 and Its Early Track Loader Design
The Bobcat 864 was introduced around the year 2000 as the company’s first foray into compact track loaders. At the time, Bobcat was transitioning from its well-established skid steer platform into rubber-tracked machines to meet growing demand for better traction and reduced ground pressure. The 864 featured a vertical lift path, a 73-horsepower diesel engine, and hydrostatic drive motors powering each track independently.
While innovative for its time, the 864 suffered from several design limitations that became apparent as machines aged. Chief among them were issues with the final drive motors, undercarriage durability, and frame rigidity under heavy use. These problems were later addressed in successor models like the T250 and T300, which offered improved reliability and resale value.
Symptoms of Drive Motor Misalignment
A common issue reported with the 864 involves the rear drive motor on one side appearing tilted or misaligned when viewed from the rear of the machine. Operators may notice that the motor leans downward relative to the lower idler pulley, and that the sprocket does not track straight with the frame. While the machine may still move, it often produces a strange noise at low speeds or under load, indicating internal stress or misalignment.
Terminology:

• Final drive motor: A hydraulic motor that powers the track sprocket, converting fluid pressure into rotational motion
  
• Idler pulley: A non-powered wheel that guides the track and maintains tension
  
• Sprocket alignment: The geometric relationship between the drive sprocket and the track frame, critical for smooth operation
  

In one case, the left-side motor was visibly angled and produced intermittent vibration. Upon removing the track, technicians discovered a broken front roller and a bent motor mounting frame, confirming structural damage.
Root Causes and Structural Implications
The misalignment is typically caused by one or more of the following:

• Worn or failed main bearing inside the final drive motor
  
• Bent motor mounting bracket or frame deformation
  
• Broken or missing undercarriage components (e.g., rollers, idlers)
  
• Impact damage from terrain or operator error
  

Once the motor housing begins to lean, it places uneven stress on the sprocket teeth and track links, accelerating wear and increasing the risk of hydraulic seal failure. If left unaddressed, the motor may detach or suffer catastrophic internal damage.
In one teardown, a technician found that the bearing had disintegrated, allowing the motor shaft to wobble and grind against the housing. The repair required full motor replacement and frame straightening.
Repair Options and Cost Considerations
Repairing a misaligned drive motor on the 864 can be costly, especially if internal damage has occurred. Options include:

• Replacing the final drive motor with a remanufactured unit (approx. $2,500–$2,700)
  
• Straightening or replacing the motor mounting frame
  
• Replacing broken rollers and inspecting all undercarriage components
  
• Realigning the sprocket and verifying hydraulic connections
  

Labor time for motor replacement typically ranges from 6 to 10 hours, depending on access and technician experience. Frame straightening may require specialized jigs or welding, and should be performed by a qualified shop to avoid compromising structural integrity.
Some operators choose to cut their losses and resell the machine at auction, especially if other components are nearing end-of-life. However, others report successful long-term use after investing in repairs and preventative maintenance.
Evaluating the 864’s Long-Term Viability
The Bobcat 864 has a mixed reputation in the industry. While some owners praise its performance and reliability when properly maintained, others view it as a transitional model with known weaknesses. The drive motors are particularly vulnerable, and resale value tends to be lower than later models.
Comparative insights:

• T250 and T300 models feature upgraded drive systems and improved frame design
  
• The 864 lacks the refined electronics and diagnostics found in newer machines
  
• Parts availability remains decent, but some components are no longer supported by Bobcat
  

One contractor with 2,500 hours on his 864 reported replacing both drive motors and tracks but experienced no other major issues. He attributed the machine’s longevity to consistent maintenance and careful operation.
Preventative Measures and Inspection Protocols
To avoid future drive motor failures:

• Inspect sprocket alignment monthly and after any impact event
  
• Monitor for unusual noises or vibration during low-speed travel
  
• Check motor mounting bolts and frame welds for signs of fatigue
  
• Replace rollers and idlers as needed to maintain track geometry
  
• Flush hydraulic fluid and inspect for contamination annually
  

Using a straightedge or laser alignment tool can help detect early signs of misalignment before visible damage occurs. Operators should also document repairs and track component wear to anticipate future needs.
Conclusion
The Bobcat 864’s drive motor misalignment is often a symptom of deeper structural or bearing failure. While repair is possible, it requires careful diagnosis and may not be cost-effective depending on the machine’s overall condition. For owners committed to restoration, addressing frame damage, replacing the motor, and reinforcing undercarriage components can restore functionality and extend service life. In compact track loaders, alignment isn’t just geometry—it’s the foundation of every forward move.