Mack Dual Steering Gearbox Relief Adjustment

[MikePhua]

Mack trucks are renowned for their durability and performance in the heavy-duty transportation industry. One of the key features of Mack trucks is their dual steering system, which is equipped with two separate steering gearboxes. Each steering gearbox controls the left and right sides of the steering system, offering increased stability and control, especially when the truck is under heavy load.
However, issues can arise in the Mack dual steering system, particularly if the relief pressure settings for the steering gearboxes are incorrect. This can lead to difficulties in steering or the steering feeling too heavy. Proper relief pressure adjustment is crucial for smooth and efficient operation of the steering system.
The Role of Relief Pressure Adjustment
Relief pressure valves are used to prevent excessive pressure from damaging the steering gearboxes or hydraulic lines. The Mack dual steering gearbox system requires proper relief pressure settings to ensure that the system functions properly, even under high load or resistance.
If the relief pressure is set too low, steering can become difficult, particularly when the truck is operating under heavy loads or at low speeds. Conversely, if the relief pressure is too high, it can overload the system, potentially causing damage to the steering components or other parts of the hydraulic system.
Steps for Adjusting Relief Pressure

1. Locate the Relief Pressure Adjustment Screw: Each steering unit in the Mack dual steering gearbox has a relief pressure adjustment screw. Begin by ensuring the truck is parked securely and the engine is turned off.
   
2. Check System Pressure: Use a pressure gauge to measure the steering system’s pressure, ensuring it falls within the manufacturer’s recommended range. Typically, the steering system pressure should be between 800 and 1200 psi.
   
3. Adjust Relief Pressure: Based on the measured pressure, use the appropriate tool to adjust the relief pressure screw. If the pressure is too high, loosen the screw slightly to reduce the pressure. If the pressure is too low, tighten the screw to increase the pressure.
   
4. Recheck the Pressure: After making adjustments, check the system pressure again to ensure it falls within the desired range. If the pressure is still too high or low, repeat the adjustment process until the correct pressure is achieved.
   
5. Test the Steering System: After adjusting, restart the truck and test the steering system. Ensure that the steering operates smoothly, without any unusual noise or excessive responsiveness.
   

Common Issues and Solutions

• Difficult Steering: If the relief pressure is set too low, steering may become more difficult. In this case, increasing the relief pressure can usually solve the issue.
  
• Overloaded Hydraulic System: If the relief pressure is too high, it can overload the hydraulic system. Lowering the relief pressure will prevent the system from becoming damaged.
  
• Unstable Steering: Incorrect adjustment may lead to unstable steering or intermittent steering failure. It is important to thoroughly test the system after each adjustment to confirm its stability.
  

Conclusion
Adjusting the relief pressure in the Mack dual steering gearboxes is essential to maintaining a smooth, responsive steering system. Properly set relief pressure not only ensures better maneuverability and control but also helps protect the system from potential overload or damage. By carefully adjusting the relief pressure and performing regular checks, the steering system can remain in optimal condition, ensuring reliable and safe operation of the truck. If problems arise, timely adjustments and tests are key to keeping the system functioning properly.