Diagnosing Cavitation and Vibration in Halitrrax Track Loaders

[MikePhua]

The Halitrrax Loader and Its Unique Configuration
Halitrrax is a lesser-known track loader brand manufactured in New Zealand, often customized for forestry, land clearing, and rugged terrain. These machines are typically fitted with hydrostatic drive systems and robust undercarriages, making them suitable for steep grades and uneven surfaces. Unlike mainstream brands such as Caterpillar or Bobcat, Halitrrax units often feature hybrid configurations, including retrofitted hydraulic components and non-standard pump assemblies.
One such example involves a Halitrrax loader equipped with a Vickers TA1919V20R hydrostatic pump, replacing the original Southcott unit. This substitution introduces compatibility challenges, especially when the plumbing and control logic are not fully adapted to the new pump’s characteristics.
Terminology Notes

• Hydrostatic Pump: A variable displacement pump that drives hydraulic motors using pressurized fluid, allowing for smooth speed control.
  
• Charge Pump: A low-pressure pump that supplies fluid to the hydrostatic system to maintain pressure and prevent cavitation.
  
• Cavitation: The formation of vapor bubbles in hydraulic fluid due to low pressure, which collapse violently and damage components.
  
• Mechanical Linkage: A physical connection between operator controls and hydraulic components, often affected by vibration and mounting flexibility.
  

Symptoms of Cavitation and Oscillation
The most alarming issue reported in retrofitted Halitrrax loaders is violent rocking of the hydrostatic pump during forward motion. This behavior resembles cavitation-induced vibration, where the pump appears to shake loose from its mounts. Key symptoms include:

• Loud grating or gear chatter during startup
  
• Severe vibration when throttle is increased
  
• Reduced or erratic forward travel
  
• Less pronounced symptoms in reverse
  
• Smooth operation when raised off the ground
  

These signs point to a combination of cavitation, mounting instability, and possible flow restriction in the charge circuit.
Root Causes and System Analysis
Several factors contribute to the instability:

• Inadequate charge pressure (measured at 190 psi, which may be borderline)
  
• Missing or clogged suction strainer in the charge line
  
• Valve block routing that introduces unnecessary resistance before the pump
  
• Worn replenishing check valves causing uneven flow
  
• Weak rubber engine mounts allowing excessive pump movement
  
• Mechanical linkage misalignment due to floating engine-pump assembly
  

A technician in Australia discovered that the original plumbing routed charge flow through a multi-function valve block before reaching the hydrostatic pump. This configuration, while functional for tilt and curl operations, introduced pressure drops and delayed replenishment under load.
Recommended Modifications and Repairs
To stabilize the system and eliminate cavitation:

• Re-route the charge line directly from the tank to the filter and then to the hydrostatic pump
  
• Replace worn rubber mounts with stiffer vibration-dampening bushings
  
• Inspect and rebuild replenishing valves using OEM or matched aftermarket kits
  
• Check for stroke-limiting slugs in the reverse control piston bore
  
• Verify that the pump’s drain port orientation matches manufacturer specs, even if mounted upside down
  

One operator reported significant improvement after bypassing the valve block and plumbing the charge line directly. The loader ran smoothly for five minutes before symptoms returned—suggesting thermal expansion or viscosity changes may also play a role.
Understanding Forward-Reverse Imbalance
Hydrostatic systems should deliver equal speed and torque in both directions unless mechanically limited. If reverse is slower or smoother, possible causes include:

• Stroke limiter installed in the reverse piston bore
  
• Uneven wear on control pistons or swash plate
  
• Flow restriction in directional control valves
  
• Replenishing valve wear affecting one circuit more than the other
  

A retired engineer in Tennessee noted that older Vickers pumps often used riveted metal tags for identification, while newer units relied on adhesive labels. Locating the ID plate is critical for sourcing correct parts, especially when the pump is mounted inverted.
Anecdote from the Field
In 2023, a land clearing crew in New South Wales retrofitted a Halitrrax loader with a surplus Vickers pump. After experiencing severe vibration, they rebuilt the linkage system and replaced all rubber mounts. The loader stabilized but still showed cavitation under heavy load. Eventually, they discovered that the suction line had collapsed internally, restricting flow. Replacing the hose resolved the issue permanently.
Preventive Measures and Long-Term Solutions

• Use high-quality hydraulic fluid with proper viscosity index
  
• Install a suction strainer if missing, sized for flow rate and micron rating
  
• Monitor charge pressure during operation and adjust relief valves as needed
  
• Replace worn check valves and springs in the replenishment circuit
  
• Avoid mismatched pump replacements without full system reconfiguration
  

Conclusion
Halitrrax loaders with retrofitted hydrostatic systems require careful attention to charge flow, mounting stability, and valve integrity. Cavitation and vibration are not just nuisances—they signal deeper compatibility and plumbing issues. With methodical diagnostics and targeted modifications, these machines can be restored to reliable service, even in demanding terrain. The key is understanding how each component interacts under load and adapting the system to match the pump’s design.