08-01-2025, 05:22 PM
Understanding the 2-Speed Travel System
The Takeuchi TB135 is a compact excavator widely respected for its maneuverability and versatility in tight construction spaces. One of its critical features is the 2-speed travel system, which allows the operator to switch between low and high-speed travel modes depending on the terrain or task requirements.
This system operates via a travel speed solenoid and associated controls, allowing hydraulic pressure to redirect flow to activate a higher gear. When this system fails, the machine becomes sluggish and stuck in low gear, reducing efficiency, especially when traveling across larger jobsites.
Common Symptoms of Malfunction
Operators typically report the following symptoms when the 2-speed system fails:
When diagnosing a 2-speed failure in a TB135, a systematic approach should be followed. Initial steps include:
The most common failure point is the travel speed solenoid valve. Located on the hydraulic valve body, it is responsible for rerouting hydraulic flow to engage high speed. Over time, this component can fail electrically (open circuit) or hydraulically (stuck spool).
Key diagnostic actions include:
In some cases, the issue lies not in the electrical system but in the hydraulic system itself. The travel motor requires a signal pressure to shift into high speed. Causes for a lack of this signal may include:
In one reported case, the cause of 2-speed failure was a secondary safety switch wired in by a previous owner to disable the function for training purposes. This highlights the importance of verifying any modifications made to the machine’s wiring system.
Another frequent mistake involves not fully depressing the travel switch or pressing it while under load. On some machines, the 2-speed function only engages when both travel levers are centered or during specific conditions (e.g., low hydraulic load, proper RPM).
Success Story: Field Fix With Simple Tools
One technician shared a story of repairing a non-functional TB135 2-speed system on-site using only a multimeter, a jumper wire, and some brake cleaner. After confirming the switch worked and voltage reached the solenoid, they pulled the solenoid, cleaned it thoroughly, and manually cycled the spool. High speed returned immediately — proof that many issues stem from contamination and not catastrophic failure.
Preventive Maintenance Recommendations
To avoid future failures of the 2-speed travel system on a TB135:
The 2-speed travel system on the Takeuchi TB135 is robust but not immune to wear, contamination, or electrical faults. With a methodical troubleshooting approach, many failures can be diagnosed and corrected quickly — even in the field. By understanding how each component contributes to high-speed operation and performing regular inspections, operators can maintain the performance and versatility that the TB135 is known for.
The Takeuchi TB135 is a compact excavator widely respected for its maneuverability and versatility in tight construction spaces. One of its critical features is the 2-speed travel system, which allows the operator to switch between low and high-speed travel modes depending on the terrain or task requirements.
This system operates via a travel speed solenoid and associated controls, allowing hydraulic pressure to redirect flow to activate a higher gear. When this system fails, the machine becomes sluggish and stuck in low gear, reducing efficiency, especially when traveling across larger jobsites.
Common Symptoms of Malfunction
Operators typically report the following symptoms when the 2-speed system fails:
- Travel speed does not change when pressing the 2-speed button.
- The machine only runs in low speed regardless of conditions.
- The indicator light for 2-speed either stays off or behaves inconsistently.
- Travel feels sluggish even when the terrain is flat and unobstructed.
When diagnosing a 2-speed failure in a TB135, a systematic approach should be followed. Initial steps include:
- Check the Travel Speed Button: Ensure the switch is not physically broken or stuck. Dirt and moisture often cause internal corrosion, making the contacts unreliable.
- Inspect the Wiring Harness: The wires running to the travel solenoid or switch could be frayed, pinched, or broken, especially in areas where the boom flexes or where the undercarriage vibrates.
- Verify Fuses and Relays: A blown fuse may prevent voltage from reaching the solenoid, effectively disabling the high-speed mode. Use a multimeter to check continuity through all relevant fuses and relays in the circuit.
The most common failure point is the travel speed solenoid valve. Located on the hydraulic valve body, it is responsible for rerouting hydraulic flow to engage high speed. Over time, this component can fail electrically (open circuit) or hydraulically (stuck spool).
Key diagnostic actions include:
- Measure Coil Resistance: Disconnect the solenoid plug and measure the coil’s resistance with a multimeter. An open circuit or unusual resistance reading indicates failure.
- Apply Direct Power: If resistance checks out, apply 12V power directly to the coil and listen for a clicking sound, which indicates activation. No click means the solenoid is either weak or stuck.
- Remove and Clean: If the solenoid activates but high-speed still does not engage, remove the solenoid and inspect for internal contamination. Rust, sludge, or small metal particles can prevent proper spool movement.
In some cases, the issue lies not in the electrical system but in the hydraulic system itself. The travel motor requires a signal pressure to shift into high speed. Causes for a lack of this signal may include:
- Clogged Pilot Line: Debris in the pilot control line may block pressure from reaching the travel motor shift port.
- Weak Charge Pressure: If charge pressure in the system is low due to worn pumps or a leaking main relief valve, the travel motor won’t shift properly.
- Faulty Check Valves or Blocked Screens: Inline screens and check valves can become obstructed, limiting flow to the control side of the travel motor. Regular maintenance helps prevent this.
In one reported case, the cause of 2-speed failure was a secondary safety switch wired in by a previous owner to disable the function for training purposes. This highlights the importance of verifying any modifications made to the machine’s wiring system.
Another frequent mistake involves not fully depressing the travel switch or pressing it while under load. On some machines, the 2-speed function only engages when both travel levers are centered or during specific conditions (e.g., low hydraulic load, proper RPM).
Success Story: Field Fix With Simple Tools
One technician shared a story of repairing a non-functional TB135 2-speed system on-site using only a multimeter, a jumper wire, and some brake cleaner. After confirming the switch worked and voltage reached the solenoid, they pulled the solenoid, cleaned it thoroughly, and manually cycled the spool. High speed returned immediately — proof that many issues stem from contamination and not catastrophic failure.
Preventive Maintenance Recommendations
To avoid future failures of the 2-speed travel system on a TB135:
- Regularly clean and inspect the solenoid valve.
- Check wiring harness condition at least quarterly.
- Use dielectric grease on connectors to resist moisture.
- Replace hydraulic filters and inspect suction screens according to schedule.
- Listen for subtle changes in travel noise, as they often signal early problems.
The 2-speed travel system on the Takeuchi TB135 is robust but not immune to wear, contamination, or electrical faults. With a methodical troubleshooting approach, many failures can be diagnosed and corrected quickly — even in the field. By understanding how each component contributes to high-speed operation and performing regular inspections, operators can maintain the performance and versatility that the TB135 is known for.
