Diagnosing Side Shift Cylinder Failure in the John Deere 570A Motor Grader

[MikePhua]

The John Deere 570A and Its Mechanical Legacy
The John Deere 570A motor grader, introduced in the late 1970s and produced through the early 1980s, was part of Deere’s push to offer mid-sized graders for municipal and light construction work. Built with mechanical simplicity and hydraulic robustness, the 570A featured a closed-center hydraulic system, mechanical linkages, and a single side-shift cylinder for moldboard positioning. Deere & Company, founded in 1837, had already established dominance in agricultural machinery and was expanding its construction equipment footprint during this period.
Though exact production numbers are unavailable, the 570A became a staple in county road departments and small contractor fleets across North America. Its reputation for reliability and ease of service has kept many units in operation decades after their release.
Symptoms of Side Shift Cylinder Failure
A common issue reported with the 570A is the sudden loss of leftward moldboard shift, while rightward movement remains functional. This failure often occurs mid-operation, with the blade stuck near full extension to one side. Operators may notice:

• Audible hydraulic effort when attempting to shift left
  
• No visible movement of the moldboard
  
• Hydraulic hoses flexing under pressure
  
• No fluid leaks or external damage
  

These symptoms suggest that the control valve is attempting to actuate the cylinder, but internal resistance or blockage is preventing movement.
Hydraulic System Overview and Control Logic
The 570A uses a closed-center hydraulic system, meaning the pump only delivers flow when a valve is opened. The side-shift function is controlled by a butterfly-style toggle that actuates a spool valve. This valve directs fluid to a single double-acting cylinder mounted behind the moldboard.
Key components include:

• Spool valve with spring-loaded centering
  
• Hydraulic cylinder with internal piston and seals
  
• Moldboard slide rails and shims
  
• Hydraulic hoses routed through the frame
  

When the valve is actuated, fluid flows to one side of the piston, extending or retracting the cylinder. If the piston seals fail or the valve is blocked, movement is restricted.
Field Diagnosis and Mechanical Testing
Operators have used several methods to diagnose the issue:

• Verifying valve linkage and spool travel compared to adjacent valves
  
• Applying external force with a come-along or ratchet strap to assist movement
  
• Monitoring hose flex and pump load during actuation
  
• Disconnecting cylinder rod end to isolate mechanical jamming
  
• Swapping hydraulic hoses with another circuit to test valve function
  

In one case, a technician applied extreme force with a come-along while actuating the valve, but the blade remained immobile. The hydraulic hose flexed and the engine loaded slightly, indicating pressure buildup but no movement—suggesting internal cylinder failure or valve blockage.
Common Causes and Solutions
Several root causes have been identified:

• Piston seal failure inside the cylinder, allowing fluid bypass
  
• Debris or contamination blocking the valve or orifice
  
• Moldboard slide jam due to packed material or folded shims
  
• Valve spool not traveling fully due to linkage misalignment
  
• Hydraulic fluid contamination or aeration
  

Recommended solutions include:

• Removing and inspecting the cylinder for seal integrity
  
• Cleaning or rebuilding the valve body and spool
  
• Loosening moldboard slide bolts and inspecting shims
  
• Grinding slide rails to restore clearance
  
• Replacing hydraulic fluid and filters
  

In one instance, prolonged operation under heavy load caused the valve to clear itself after several hours, suggesting that heat and fluid velocity dislodged internal debris.
Shim Adjustment and Moldboard Slide Maintenance
The moldboard slide system uses shims to maintain tightness and reduce play. Over time, wear concentrates in the center six feet of the slide, while the ends remain relatively unworn. Improper shim placement can cause binding at full extension.
Best practices include:

• Shimming with the blade fully shifted to one side, not centered
  
• Removing folded or damaged shims
  
• Grinding slide rails lightly to restore uniform clearance
  
• Using conveyor belting or protective covers to shield the slide from debris
  

One operator noted a 3/16" gap between the slide and retainer, which caused sticking at full extension. After removing shims and applying pressure with the lean wheel, the blade retracted smoothly.
Manufacturer History and Equipment Context
John Deere’s grader lineup evolved from the 570A to the 570B and later the G and GP series, incorporating electronic controls and advanced hydraulics. The 570A remains a favorite among vintage equipment enthusiasts due to its mechanical transparency and rebuildable components.
While newer graders use wear inserts and composite slide materials, the 570A relies on steel-on-steel contact, requiring periodic adjustment and lubrication. Technical manuals from the era often omit detailed slide restoration procedures, leaving operators to rely on field experience and fabrication.
Conclusion
Side shift cylinder failure in the John Deere 570A is often a combination of hydraulic obstruction and mechanical wear. Through methodical testing, inspection, and adjustment, operators can restore full moldboard functionality without major component replacement. The 570A’s enduring service life is a testament to its design—and to the ingenuity of those who keep it running. With proper care, even a decades-old grader can deliver precision and performance on today’s roads.