Vermeer T655 Trencher Troubleshooting and Operational Insights

[MikePhua]

The Vermeer T655 and Its Role in Utility Trenching
Vermeer Corporation, founded in 1948 in Pella, Iowa, has long been a leader in specialized equipment for underground construction, pipeline installation, and surface mining. The T655 trencher is part of Vermeer’s Terrain Leveler and utility trencher lineup, designed for mid-range trenching applications such as fiber optic installation, water lines, and gas pipelines. With a reputation for durability and precision, the T655 has been deployed across North America, Europe, and Asia in both urban and remote infrastructure projects.
The T655 typically features a Cummins turbocharged diesel engine producing around 250 horsepower, a hydrostatic drive system, and a chain trencher capable of cutting depths up to 6 feet depending on boom configuration. Its modular design allows for quick adaptation to different soil types and trench widths.
Core Components and Hydraulic Behavior
The T655’s performance relies heavily on its hydraulic system, which powers the trencher boom, conveyor, stabilizers, and auxiliary functions. The system includes:

• Dual hydraulic pumps for independent circuit control
  
• Proportional control valves for smooth actuation
  
• Pressure relief valves to protect components
  
• Return filters and suction strainers for fluid cleanliness
  
• Pilot control joysticks with integrated safety lockouts
  

Operators may encounter issues when hydraulic flow is interrupted, pressure drops unexpectedly, or actuators fail to respond. These symptoms often point to contamination, seal wear, or electrical faults in solenoid-controlled valves.
Terminology Notes

• Hydrostatic Drive: A transmission system using hydraulic fluid to transfer power from engine to tracks or wheels.
  
• Pilot Control: A low-pressure hydraulic signal used to actuate main control valves.
  
• Relief Valve: A safety valve that limits maximum hydraulic pressure to prevent damage.
  
• Return Filter: A filter that cleans hydraulic fluid before it returns to the reservoir.
  
• Boom Assembly: The structural arm that supports the cutting chain and determines trench depth.
  

Common Operational Challenges and Field Symptoms
Operators have reported several recurring issues:

• Trencher boom fails to raise or lower smoothly
  
• Conveyor belt stalls under load
  
• Hydraulic fluid overheating during extended cuts
  
• Chain speed fluctuates or stalls intermittently
  
• Stabilizers do not respond to joystick input
  

In one fiber trenching project in Saskatchewan, a T655 began losing boom responsiveness after two hours of continuous operation. Technicians discovered that the return filter was clogged, causing backpressure and sluggish valve response. After replacing the filter and flushing the system, performance returned to normal.
Diagnostic Strategy and Maintenance Recommendations
To troubleshoot hydraulic faults:

• Check fluid level and inspect for discoloration or foaming
  
• Test system pressure at key ports using calibrated gauges
  
• Inspect electrical connectors at solenoid valves for corrosion
  
• Clean or replace return filters and suction strainers
  
• Verify joystick signal continuity and pilot pressure
  
• Inspect hoses for abrasion, kinks, or internal collapse
  

Preventive measures:

• Replace hydraulic filters every 500 hours or quarterly
  
• Flush fluid annually or after contamination events
  
• Torque valve block bolts to spec and check for leaks
  
• Use OEM-grade fluid with anti-wear additives
  
• Train operators on warm-up procedures and load management
  

In one municipal fleet in Florida, implementing a hydraulic inspection checklist reduced downtime by 40% and extended pump life by 25%.
Mechanical Adjustments and Chain Tensioning
The cutting chain requires regular inspection and tensioning to maintain trenching efficiency. Recommendations include:

• Check chain tension daily and adjust via boom-mounted tensioner
  
• Inspect teeth for wear and replace in matched sets
  
• Grease boom pivot points and sprocket bearings every 50 hours
  
• Monitor chain alignment and guide wear
  
• Replace worn sprockets to prevent chain jump or derailment
  

In a rocky soil trenching job in Nevada, technicians found that uneven tooth wear was causing chain vibration and premature bearing failure. Switching to carbide-tipped teeth and balancing the chain resolved the issue.
Electrical System and Control Panel Behavior
The T655 includes a digital control panel with fault indicators, engine diagnostics, and hydraulic status readouts. Electrical faults may manifest as:

• Warning lights for low pressure or high temperature
  
• Unresponsive joysticks or control switches
  
• Intermittent power loss to actuators
  
• Fault codes related to sensor inputs or CAN-bus communication
  

Solutions include:

• Inspecting fuses and relays for continuity
  
• Cleaning ground straps and battery terminals
  
• Replacing damaged wiring harness sections
  
• Updating firmware if available from Vermeer support
  
• Resetting control panel after component replacement
  

In one trenching crew in Illinois, a faulty ground connection caused false low-pressure warnings. After re-terminating the ground strap and reseating the connectors, the system stabilized.
Final Thoughts
The Vermeer T655 trencher is a powerful and adaptable machine, but its performance depends on the health of its hydraulic and electrical systems. From chain tension to pilot valve response, each subsystem plays a role in delivering clean, consistent trenching. With methodical diagnostics, preventive care, and operator training, the T655 can tackle tough soils and long runs with confidence. In the world of underground infrastructure, precision starts with the cut—and the T655 is built to deliver it.