Troubleshooting the 1975 CAT 955L: No Hydraulics or Drive

[MikePhua]

The Caterpillar 955L track loader, manufactured in the 1970s, is known for its rugged reliability and high-performance capabilities in tough work environments. However, like any heavy machinery, it is not immune to malfunctions over time. A common issue that has surfaced with the 955L involves a complete failure of the hydraulics and drive systems, which can significantly affect performance and operations. In this article, we will explore the potential causes behind this problem, common troubleshooting methods, and how to avoid these issues in the future.
Overview of the 1975 CAT 955L
The 955L is a part of Caterpillar's L-series of track loaders, and it features a powerful engine capable of handling a wide range of tasks, from excavation to material handling. It is particularly useful in construction, mining, and demolition projects where rugged durability is required. Despite being an older model, the 955L continues to be a staple in many fleets, thanks to its durable design and ease of repair.
However, like many older machines, the 955L can experience issues with its hydraulics and drive systems, which, if not addressed, can lead to significant downtime and costly repairs.
Common Problem: No Hydraulics or Drive
A common issue with the 1975 CAT 955L is a complete loss of hydraulic function or drive power. This problem can occur suddenly, causing the loader to lose both the ability to move and perform critical tasks like lifting or digging. Understanding the underlying causes of these failures is crucial for effective troubleshooting.
1. Hydraulic System Failure
The hydraulic system in the 955L plays a vital role in controlling the loader's lifting, steering, and other key functions. If the hydraulics fail, the loader will lose its ability to operate normally. A few common causes of hydraulic failure in older equipment like the 955L are:

• Hydraulic Fluid Contamination: Over time, dirt, debris, and moisture can contaminate the hydraulic fluid, causing blockages or excessive wear on the pump, valves, and hoses.
  
• Pump Failure: The hydraulic pump is the heart of the system, providing the necessary pressure to power the hydraulic cylinders. If the pump fails, hydraulic pressure is lost, and the loader will be unable to lift, move, or perform other critical functions.
  
• Leaks in the System: Leaks in the hydraulic lines or seals can result in low hydraulic fluid levels, leading to insufficient pressure and failure of the hydraulic system.
  

Troubleshooting Tips:

• Check the hydraulic fluid level and condition. If the fluid appears dirty or contaminated, it may need to be replaced.
  
• Inspect the hydraulic hoses for signs of wear, cracks, or leaks.
  
• Test the hydraulic pump pressure using a pressure gauge to determine if the pump is functioning correctly.
  
• Replace any worn-out seals or damaged parts.
  

2. Drive System Failure
In addition to the hydraulic failure, the CAT 955L may experience issues with the drive system, which includes the transmission, differential, and the drive motor. Loss of drive power can make the loader immobile and unable to complete tasks.
Some common causes of drive system failure include:

• Transmission Fluid Low or Contaminated: If the transmission fluid is low or contaminated with dirt or metal shavings, the gears may fail to engage, leading to a loss of drive power.
  
• Faulty Drive Motors: The drive motors, which are responsible for powering the tracks, can become worn over time, leading to a loss of traction and movement.
  
• Hydraulic Drive System Issues: In some cases, the hydraulic system is directly tied to the drive system. A failure in the hydraulic system, such as a drop in pressure or pump failure, can also cause a loss of drive.
  

Troubleshooting Tips:

• Check the transmission fluid level and condition. If the fluid is low or contaminated, replace it with fresh fluid.
  
• Inspect the drive motors for signs of wear or damage. If a motor is faulty, it may need to be replaced or rebuilt.
  
• Test the hydraulic drive system to ensure that it is providing the necessary pressure to the drive motors.
  

Other Possible Causes of Failure
While hydraulic and drive system failures are the most common issues, there are other potential causes that should be considered when diagnosing the problem:
Electrical System Malfunctions
The electrical system controls various functions of the CAT 955L, including starting, lighting, and system diagnostics. If there is an electrical failure, it may prevent the loader from starting or cause it to lose functionality.
Troubleshooting Tip:

• Check the battery, alternator, and wiring for any loose connections or damaged components. If the electrical system is faulty, repairs may involve replacing the battery or rewiring the system.
  

Control Valve Problems
The control valves regulate the flow of hydraulic fluid throughout the system. If these valves become clogged or malfunction, it can prevent hydraulic fluid from reaching critical components like the lift cylinders or drive motors.
Troubleshooting Tip:

• Inspect the control valves for signs of clogging or damage. Clean or replace any faulty valves to restore proper hydraulic function.
  

Preventative Maintenance for the CAT 955L
To avoid the issues related to hydraulics and drive failure, regular maintenance is essential. Here are some key maintenance practices to keep the 955L running smoothly:
1. Regular Hydraulic System Checks

• Regularly check the hydraulic fluid level and condition.
  
• Change the hydraulic fluid and replace filters every 500 hours of operation to prevent contamination.
  
• Inspect the hydraulic lines and fittings for leaks or wear.
  

2. Transmission Fluid Maintenance

• Check the transmission fluid level and condition regularly.
  
• Change the fluid every 1,000 hours of operation to maintain smooth shifting and prevent transmission problems.
  
• Inspect the transmission for signs of damage or excessive wear.
  

3. Drive Motor Inspections

• Periodically inspect the drive motors for leaks, wear, and unusual noises.
  
• Ensure the drive belts are properly tensioned and replaced when necessary.
  

4. Electrical System Care

• Regularly inspect the battery, wiring, and alternator to ensure the electrical system is functioning correctly.
  
• Keep connections clean and free from corrosion.
  

Conclusion: Addressing CAT 955L Hydraulic and Drive Failures
The CAT 955L is a powerful and reliable piece of equipment, but like all machines, it requires proper care and maintenance to ensure long-term functionality. Hydraulic and drive system failures can severely affect performance, but with the right troubleshooting methods, many of these issues can be resolved. Regular inspections, fluid changes, and timely repairs will keep the CAT 955L running smoothly and help prevent future breakdowns.
If you experience issues with the hydraulics or drive system, don't hesitate to follow the diagnostic steps mentioned or consult with a professional technician for more advanced repairs. With careful attention to maintenance and early detection of potential issues, the CAT 955L can continue to be a valuable asset in your fleet for many years to come.