Diagnosing Steering Stutter and Hydraulic Lag in the CAT TH255C Telehandler

[MikePhua]

The TH255C and Its Compact Versatility
The Caterpillar TH255C telehandler was designed for tight job sites and light material handling, offering a compact frame, four-wheel steering, and a lift capacity of around 5,500 lbs. Introduced in the early 2010s, it filled a niche for contractors needing reach and maneuverability without the bulk of larger telehandlers. With a boom reach of over 18 feet and a turning radius under 12 feet, the TH255C became popular in agriculture, landscaping, and urban construction.
Its hydrostatic drive and load-sensing hydraulic system allow precise control, but also introduce complexity. When steering or boom functions begin to stutter or lag, the issue often lies in the interaction between hydraulic pressure, fluid temperature, and mechanical wear.
Symptoms of Steering Stutter and Popping
Operators have reported a distinct stutter or popping sensation when turning the wheels left or right. This behavior is most pronounced when the machine is warm and under load. Interestingly, the issue disappears when the telehandler is stationary or held at full steering lock, suggesting that the problem is dynamic rather than static.
In addition, boom functions—especially simultaneous up/down and in/out movements—become sluggish or even stop entirely when the machine is hot. These symptoms point to a hydraulic system struggling to maintain pressure across multiple circuits.
Terminology Clarification
- Hydrostatic Drive: A propulsion system using hydraulic fluid to power wheel motors
- Load-Sensing Hydraulics: A system that adjusts pump output based on demand from control valves
- Spider Gears: Small gears inside a differential that allow wheels to rotate at different speeds
- Limited Slip Differential: A mechanism that limits wheel speed differences to improve traction
- Relief Valve: A hydraulic component that limits system pressure to prevent damage
Mechanical and Hydraulic Inspection Points
Initial suspicion often falls on worn universal joints, but in this case, all U-joints were tight. When the telehandler was lifted on jack stands, the stutter vanished—suggesting that tire friction or drivetrain load may be contributing. However, the issue persisted even when parked on gravel or dirt, ruling out tire grab.
One technician suggested checking the spider gears in the differential. If these gears are damaged or missing teeth, they can cause intermittent binding during turns. Removing the drain plug and inspecting for metal fragments is a quick way to confirm gear failure.
Another possibility is a failing relief valve in the hydraulic system. If the valve cannot maintain pressure under load, steering and boom functions may stutter or stall. Testing hydraulic pressure at designated ports can reveal whether the system is dropping below operational thresholds.
Limited Slip Additive and Brake Chatter
Some telehandlers are equipped with limited slip differentials that require friction modifiers—additives that reduce chatter and improve gear engagement. Without these additives, the brakes may grab or vibrate during turns, mimicking a steering stutter. Adding a dose of limited slip additive to the axle oil has resolved similar issues in other CAT machines.
Field Anecdotes and Operator Experience
A technician in Pennsylvania recalled a CAT telehandler that exhibited brake chatter during turns. After adding limited slip additive, the issue disappeared. Another operator in Australia diagnosed a steering stutter as a spider gear failure after finding gear fragments in the differential housing.
These stories highlight the importance of combining hydraulic diagnostics with mechanical inspection. Telehandlers operate under complex load conditions, and symptoms often overlap between systems.
Recommended Diagnostic Steps
To isolate the cause of steering stutter and hydraulic lag:

• Inspect spider gears by draining the differential and checking for metal debris
  
• Test hydraulic pressure at steering and boom control ports
  
• Check fluid temperature and viscosity after warm-up
  
• Add limited slip additive to axle oil if applicable
  
• Verify relief valve operation and replace if pressure drops under load
  
• Inspect brake components for chatter or uneven wear
  

Preventive Maintenance Tips
To avoid future steering and hydraulic issues:

• Change hydraulic fluid and filters every 500 hours
  
• Use manufacturer-approved fluids and additives
  
• Monitor system pressure during operation
  
• Keep axle oil clean and topped off
  
• Inspect U-joints and steering linkages quarterly
  

Final Thoughts
The CAT TH255C telehandler is a nimble and capable machine, but its compact design means that hydraulic and mechanical systems are tightly integrated. Steering stutter and boom lag are often symptoms of deeper pressure or gear issues. With a methodical approach—combining fluid analysis, pressure testing, and mechanical inspection—operators can restore smooth performance and extend the life of their equipment. In the world of telehandlers, precision starts with pressure—and ends with traction.