Terex TA35 Forward Motion Issues

[MikePhua]

The Terex TA35 is a popular articulated hauler used in various heavy-duty construction, mining, and transportation tasks. Known for its robustness and high payload capacity, this vehicle is often the go-to choice for operators who require a durable machine capable of handling rough terrains and challenging work conditions. However, like all heavy machinery, it can face issues, including the common problem of failure to move forward while being able to reverse. Understanding the potential causes of this issue and how to address it is essential to minimize downtime and keep the Terex TA35 operating efficiently.
Overview of the Terex TA35 Articulated Hauler
The Terex TA35 is an articulated dump truck (ADT) designed for off-road, high payload capacity tasks. It features a robust drivetrain, high ground clearance, and excellent maneuverability, making it ideal for use in construction sites, quarries, and mining operations. It can handle a wide variety of materials and can carry large payloads in harsh environments.
However, one of the common issues operators might face is the machine's failure to move forward while it is still able to reverse. This issue can arise from several sources within the machine's mechanical and hydraulic systems.
Possible Causes of the Issue
When a Terex TA35 exhibits the problem of moving in reverse but not forward, it indicates a malfunction in the drive system, which can be attributed to various factors. Some of the most common causes include:

1. Transmission or Gearbox Malfunction
   • Symptoms: The machine moves in reverse but fails to move forward.
     
   • Cause: A faulty or damaged transmission can prevent the forward gear from engaging correctly. This can happen due to worn-out clutch plates, failed solenoids, or issues with the transmission fluid. A clogged or low transmission fluid level could also contribute to the malfunction.
     
   • Solution: Inspect the transmission and gearbox for any signs of wear or damage. Check the fluid levels and replace or top-up the transmission fluid. If the clutch plates or solenoids are damaged, they will need to be replaced.
     
2. Hydraulic System Issues
   • Symptoms: The machine fails to move forward but operates in reverse.
     
   • Cause: The Terex TA35 uses a hydraulic system to engage the drive. If there is an issue with the hydraulic pumps, valves, or the oil quality, the vehicle might not be able to engage forward motion. Low hydraulic fluid levels, air in the system, or a malfunctioning hydraulic valve could all lead to the problem.
     
   • Solution: Check the hydraulic fluid levels and ensure that there are no leaks in the system. Inspect the hydraulic pump for wear and replace any faulty valves. Bleeding the hydraulic system to remove air may also resolve the issue.
     
3. Drive Shaft or Axle Problems
   • Symptoms: The machine engages reverse but does not move forward, with no noticeable sounds or grinding.
     
   • Cause: A damaged or disconnected drive shaft or faulty axle could cause the forward motion to fail while still allowing reverse movement. This could result from a broken coupling, worn axle joints, or a damaged differential.
     
   • Solution: Inspect the drive shafts and axles for any visible damage or loose connections. If there is a problem with the differential or axle joints, replacing the damaged parts will be necessary.
     
4. Electronic Control System Failure
   • Symptoms: The machine will not engage forward motion but can reverse without issue.
     
   • Cause: The Terex TA35 is equipped with an electronic control system that manages the machine’s functions. A malfunctioning control unit, sensor, or wiring could lead to the failure to engage the forward gears. This could also be caused by a damaged transmission control module (TCM) or faulty switches.
     
   • Solution: Inspect the electronic control system, including the wiring and sensors. Use diagnostic equipment to check for error codes in the system and repair or replace any faulty electronic components.
     
5. Clutch or Brake Issues
   • Symptoms: The vehicle works in reverse but does not move forward when the accelerator is engaged.
     
   • Cause: A malfunctioning clutch or brakes can also prevent forward motion. If the clutch does not disengage properly, it could prevent the forward gear from engaging. Additionally, if the brake system is seized or malfunctioning, it could prevent the truck from moving forward.
     
   • Solution: Check the clutch operation and ensure it is fully disengaging when switching gears. Inspect the brake system for any signs of seizing or malfunction and ensure that the brake pads and discs are in good condition.
     

Diagnostic and Repair Steps
To diagnose and fix the issue of a Terex TA35 that moves in reverse but not forward, follow these steps:

1. Perform Visual Inspection
   Start by performing a visual inspection of the vehicle’s drive system, looking for any obvious signs of leaks, loose parts, or damage. Check the hydraulic lines and fluid levels, and ensure there are no blockages in the system.
   
2. Check Hydraulic Fluid and Components
   Ensure that the hydraulic fluid is at the proper level and that it is clean. If the fluid appears dirty or contaminated, perform a fluid change. Inspect the hydraulic pumps and valves for wear or damage, as well as the control solenoids.
   
3. Examine the Transmission and Gearbox
   Check the transmission fluid levels and look for any signs of fluid leakage. If the fluid level is low, refill it and check for any issues such as burnt fluid or metal shavings that could indicate internal damage. Inspect the gearbox and clutch components for any signs of wear.
   
4. Inspect the Drive Shaft and Axles
   Ensure that the drive shaft and axles are properly connected and free from damage. Check the differential and axle joints for any signs of wear or breakage.
   
5. Test the Electrical and Control System
   Use diagnostic tools to check the electronic control system for error codes. Inspect wiring, sensors, and switches for proper function. If necessary, replace any damaged or malfunctioning components.
   
6. Test Run After Repairs
   Once the necessary repairs have been made, perform a test run of the machine to verify that the forward motion is working properly. Test the machine under load to ensure that all systems are functioning correctly and that the issue is fully resolved.
   

Conclusion
When a Terex TA35 goes into reverse but fails to move forward, it typically indicates an issue within the transmission, hydraulic system, or drive system. Diagnosing the problem systematically by checking the hydraulic fluid, transmission, drive shafts, and electronic control systems can help pinpoint the root cause. Regular maintenance and timely repairs are essential to prevent such issues from arising and to ensure that the Terex TA35 remains a reliable asset for your operations.
By maintaining the hydraulic system, transmission, and control electronics, operators can minimize downtime and extend the life of their equipment. Taking care of these key components will ensure smooth operation in both forward and reverse gears.