Reinstalling and Bleeding Deck Turn Rams on DRMCO Motor Graders

[MikePhua]

The DRMCO Blade Rotation System and Its Mechanical Design
DRMCO motor graders, though no longer in mainstream production, remain in service across Australia and New Zealand due to their rugged build and straightforward mechanical systems. One of the more nuanced components of these graders is the deck turn mechanism, which allows the moldboard (blade) to rotate horizontally for angled grading. This rotation is controlled by hydraulic cylinders known as deck turn rams.
These rams are mounted between the grader frame and the crank arms that pivot the blade. When activated, they extend or retract to rotate the moldboard. Over time, the seals within these rams degrade, leading to hydraulic leaks, loss of pressure, and erratic blade movement. Replacing the seals is a common maintenance task, but reinstalling the rams and bleeding air from the system requires precision to avoid damaging the crank arms or misaligning the blade.
Preparation and Safety Before Reinstallation
Before removing or reinstalling deck turn rams, the blade must be securely grounded. This prevents unintended movement and ensures that the crank arms remain in a fixed position. If the blade shifts while the rams are disconnected, the crank arms can rotate independently, making reinstallation difficult and potentially hazardous.
Operators should:

• Lower the blade fully to the ground
  
• Shut down the hydraulic system and relieve pressure
  
• Mark the crank arm positions to preserve alignment
  
• Inspect the ram mounting points for wear or distortion
  

In one case, a grader operator in Narrabri, NSW, noted that keeping the blade stationary during ram removal simplified the reinstallation process significantly. The crank arms remained aligned, and the hydraulic system could be re-pressurized without mechanical interference.
Reinstallation Procedure and Air Bleeding Technique
Once the new seals are installed and the rams are ready for reattachment, the following steps are recommended:

• Connect the rear end of each ram to the grader frame
  
• Use the hydraulic system to extend the rams slowly
  
• Loosen the hydraulic fittings slightly to allow trapped air to escape
  
• Manually push the ram rods back in until they align with the crank arm mounting points
  
• Reattach the front ends of the rams to the crank arms
  
• Tighten all hydraulic fittings and test the system under low pressure
  

This method allows air to bleed out gradually while maintaining control over ram movement. It also prevents hydraulic lock or erratic extension, which can damage the crank arms or misalign the blade.
Terminology annotation:

• Bleeding: The process of removing trapped air from hydraulic lines or cylinders
  
• Crank arm: A pivoting lever that translates hydraulic motion into blade rotation
  
• Hydraulic fitting: A connector that joins hoses or pipes to hydraulic components
  

Avoiding Common Mistakes and Misalignments
One of the most frequent errors during reinstallation is attempting to force the ram rods into position without hydraulic assistance. This can bend the rods or damage the seals. Another mistake is failing to bleed the system properly, leading to spongy or delayed blade response.
To avoid these issues:

• Always use controlled hydraulic pressure to extend or retract the rams
  
• Never torque fittings while under pressure
  
• Use thread sealant sparingly to avoid contamination
  
• Cycle the blade rotation several times after installation to ensure full range of motion
  

In one field repair, a technician attempted to reinstall the rams with the blade slightly elevated. The crank arms had shifted, and the ram rods could not be aligned. After lowering the blade and resetting the crank arms manually, the installation proceeded smoothly.
Hydraulic System Behavior and Long-Term Maintenance
Hydraulic systems in older graders like DRMCO models are sensitive to contamination and air ingress. After any repair involving cylinder removal, the system should be flushed and refilled with clean hydraulic fluid. Filters should be inspected and replaced if necessary.
Recommended maintenance intervals:

• Hydraulic fluid change: Every 1,000 hours or annually
  
• Seal inspection: Every 500 hours or during seasonal service
  
• Ram rod lubrication: Monthly, especially in dusty environments
  
• Fitting torque check: After 10 hours of operation post-repair
  

Operators should also monitor for signs of internal leakage, such as fluid bypassing the seals or inconsistent blade movement. These symptoms may indicate improper seal installation or worn cylinder walls.
Lessons from the Field and Practical Advice
A grader operator in New Zealand shared that after reinstalling deck turn rams, he noticed a slight delay in blade rotation. Upon inspection, he found that one hydraulic fitting had not been fully tightened, allowing air to re-enter the system. After correcting the fitting and re-bleeding the ram, the blade responded instantly.
Another technician recalled a DRMCO grader used in flood recovery work, where the deck turn rams were repeatedly exposed to water and mud. Seal failure became frequent, prompting the team to install aftermarket wipers and protective boots on the ram rods. This extended seal life and reduced downtime.
Conclusion
Reinstalling and bleeding deck turn rams on DRMCO motor graders is a task that demands mechanical precision and hydraulic awareness. By grounding the blade, aligning crank arms, and using controlled hydraulic pressure, operators can restore full blade rotation without risking damage. With proper technique and preventative maintenance, these legacy machines continue to perform reliably in demanding conditions, proving that even older equipment can be kept in top shape with thoughtful care and field-tested wisdom.