Replacing the Orbital Steering Valve on the Lull 644TT-34 Highlander II Telehandler

[MikePhua]

The Lull 644TT-34 Highlander II telehandler, a robust piece of equipment introduced by JLG Industries, has been a staple in construction and material handling since its debut. With a lift capacity of 6,000 lbs and a maximum lift height of 34 feet, it offers versatility and power for various tasks. However, like all machinery, its components, such as the orbital steering valve, can wear out over time, leading to steering issues.
Understanding the Orbital Steering Valve
The orbital steering valve is a crucial component in the hydraulic steering system of the telehandler. It translates the driver's steering input into hydraulic pressure, directing fluid to the steering cylinders, which in turn move the wheels. A malfunctioning valve can result in erratic or unresponsive steering, posing safety risks on the job site.
Identifying Symptoms of a Faulty Steering Valve
Common signs of a failing orbital steering valve include:

• Unresponsive Steering: Difficulty in turning the steering wheel or delayed wheel movement.
  
• Erratic Steering Behavior: Wheels turning unpredictably or not returning to center.
  
• Hydraulic Fluid Leaks: Visible leaks around the valve or steering cylinders.
  
• Increased Steering Effort: Heavier than usual steering, indicating potential internal resistance.
  

If these issues arise, it's imperative to inspect the orbital steering valve promptly to prevent further damage and ensure operator safety.
Steps to Replace the Orbital Steering Valve

1. Safety Precautions: Before beginning, ensure the telehandler is on a stable surface, the engine is off, and the hydraulic pressure is relieved.
   
2. Locate the Valve: The orbital steering valve is typically mounted on the steering column or near the steering cylinders. Refer to the Lull 644TT-34 service manual for precise location details.
   
3. Disconnect Hydraulic Lines: Carefully disconnect the hydraulic lines from the valve, using appropriate tools to prevent damage.
   
4. Remove the Faulty Valve: Unbolt and remove the old valve from its mounting position.
   
5. Install the New Valve: Position the new orbital steering valve and secure it with bolts.
   
6. Reconnect Hydraulic Lines: Attach the hydraulic lines to the new valve, ensuring all connections are tight and leak-free.
   
7. Bleed the System: Activate the steering system to remove any air trapped in the hydraulic lines, ensuring smooth operation.
   
8. Test the Steering: Operate the telehandler to verify that the steering functions correctly and there are no leaks.
   

Sourcing a Replacement Orbital Steering Valve
Replacement valves can be sourced from various suppliers:

• OEM Parts: Original Equipment Manufacturer parts ensure compatibility and reliability.
  
• Aftermarket Suppliers: Companies like Eaton, Char-Lynn, and Danfoss offer compatible orbital steering valves.
  
• Used Parts: For budget-conscious operators, used valves from reputable dealers can be a viable option.
  

When selecting a replacement, ensure it matches the specifications of the original valve to maintain optimal performance.
Maintenance Tips to Prolong Valve Life

• Regular Inspections: Periodically check for signs of wear or leaks around the steering system.
  
• Hydraulic Fluid Maintenance: Use the recommended hydraulic fluid and change it at intervals specified in the service manual.
  
• Seal Checks: Inspect seals for wear and replace them as needed to prevent contamination.
  
• Avoid Overloading: Operating within the telehandler's rated capacity reduces strain on the steering system.
  

Real-World Considerations
Operators have reported that addressing steering issues promptly not only restores functionality but also enhances safety on the job site. For instance, one operator noted that after replacing the orbital steering valve, the telehandler's maneuverability improved significantly, reducing the risk of accidents.
Conclusion
The orbital steering valve plays a pivotal role in the Lull 644TT-34 Highlander II telehandler's performance. Regular maintenance and timely replacement of this component ensure smooth operation and safety. By following the outlined steps and sourcing quality replacement parts, operators can keep their equipment running efficiently for years to come.