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The John Deere 500A and Its Hydraulic Legacy
The John Deere 500A was part of Deere’s industrial tractor and backhoe lineup during the 1970s, designed for utility contractors, municipalities, and agricultural users needing a reliable digging and loading machine. Built with a mechanical transmission and a robust hydraulic system, the 500A featured a front-mounted hydraulic pump driven directly from the crankshaft, supplying fluid to the loader, backhoe, steering, and transmission functions.
Despite its age, the 500A remains in service across North America, often passed down through generations or acquired by enthusiasts restoring vintage equipment. Its hydraulic system, while simple by modern standards, is highly dependent on proper fluid flow, charge pressure, and mechanical linkages.
Symptoms of Hydraulic Failure After Long-Term Storage
A common issue with machines like the 500A is complete hydraulic failure after extended periods of inactivity. In one case, a unit sat for five years after running out of fuel. Once the engine was restarted—following a rebuild of the injection pump—none of the hydraulic functions responded. This included the power steering, transmission, loader, and backhoe.
Initial checks confirmed that the hydraulic fluid level was adequate and the front shaft driving the pump was rotating. However, the system remained unresponsive, pointing to a deeper issue in the hydraulic circuit or control linkages.
Understanding the Hydraulic Charge System
The 500A uses a radial variable displacement pump that relies on charge pressure supplied by a transmission-mounted pump. This charge pressure feeds the main hydraulic pump, which then distributes fluid to the rest of the system. If the transmission pump fails or is starved of oil, the entire hydraulic system will shut down.
Key components to inspect include:
In one successful diagnosis, the root cause was traced to the clutch disconnect lever located near the dash. This lever, when pulled back, disengages the transmission clutch, effectively halting hydraulic pressure. The lever had a mechanical stop connected to a dash-mounted knob, preventing full engagement. Once the knob was pulled and the lever pushed forward, hydraulic functions were instantly restored.
This highlights a critical lesson: mechanical linkages and control levers, especially those rarely used, can become stuck or misaligned over time. A simple obstruction or forgotten setting can mimic catastrophic failure.
Preventive Measures and Service Recommendations
To avoid similar issues:
Hydraulic failure on a John Deere 500A is often not a failure at all, but a mechanical oversight. Machines that sit idle for years may develop stuck linkages, clogged screens, or forgotten settings that interrupt fluid flow. By understanding the charge pressure system and inspecting control levers like the clutch disconnect, operators can restore full function without major repairs. The 500A remains a testament to Deere’s durable engineering, and with proper care, it continues to serve decades after its production ended.
The John Deere 500A was part of Deere’s industrial tractor and backhoe lineup during the 1970s, designed for utility contractors, municipalities, and agricultural users needing a reliable digging and loading machine. Built with a mechanical transmission and a robust hydraulic system, the 500A featured a front-mounted hydraulic pump driven directly from the crankshaft, supplying fluid to the loader, backhoe, steering, and transmission functions.
Despite its age, the 500A remains in service across North America, often passed down through generations or acquired by enthusiasts restoring vintage equipment. Its hydraulic system, while simple by modern standards, is highly dependent on proper fluid flow, charge pressure, and mechanical linkages.
Symptoms of Hydraulic Failure After Long-Term Storage
A common issue with machines like the 500A is complete hydraulic failure after extended periods of inactivity. In one case, a unit sat for five years after running out of fuel. Once the engine was restarted—following a rebuild of the injection pump—none of the hydraulic functions responded. This included the power steering, transmission, loader, and backhoe.
Initial checks confirmed that the hydraulic fluid level was adequate and the front shaft driving the pump was rotating. However, the system remained unresponsive, pointing to a deeper issue in the hydraulic circuit or control linkages.
Understanding the Hydraulic Charge System
The 500A uses a radial variable displacement pump that relies on charge pressure supplied by a transmission-mounted pump. This charge pressure feeds the main hydraulic pump, which then distributes fluid to the rest of the system. If the transmission pump fails or is starved of oil, the entire hydraulic system will shut down.
Key components to inspect include:
- Pump coupling: Ensures the pump is physically rotating
- Transmission disconnect lever: Disengages the clutch, cutting off hydraulic drive
- Suction screen and filter: Can become clogged with debris or sludge
- Stroke control valve: May stick due to varnish or corrosion
In one successful diagnosis, the root cause was traced to the clutch disconnect lever located near the dash. This lever, when pulled back, disengages the transmission clutch, effectively halting hydraulic pressure. The lever had a mechanical stop connected to a dash-mounted knob, preventing full engagement. Once the knob was pulled and the lever pushed forward, hydraulic functions were instantly restored.
This highlights a critical lesson: mechanical linkages and control levers, especially those rarely used, can become stuck or misaligned over time. A simple obstruction or forgotten setting can mimic catastrophic failure.
Preventive Measures and Service Recommendations
To avoid similar issues:
- Always inspect and exercise all control levers before diagnosing hydraulic faults
- Drain and replace hydraulic fluid every 1,000 hours or 2 years
- Clean suction screens and replace filters during annual service
- Lubricate mechanical linkages and check for rust or binding
- Keep a service manual on hand for reference—reprints are widely available
Hydraulic failure on a John Deere 500A is often not a failure at all, but a mechanical oversight. Machines that sit idle for years may develop stuck linkages, clogged screens, or forgotten settings that interrupt fluid flow. By understanding the charge pressure system and inspecting control levers like the clutch disconnect, operators can restore full function without major repairs. The 500A remains a testament to Deere’s durable engineering, and with proper care, it continues to serve decades after its production ended.
