Diagnosing Transmission Pump Failure on the John Deere 310A Backhoe

[MikePhua]

The 310A and Its Role in Compact Construction
The John Deere 310A was introduced in the late 1970s as part of Deere’s early backhoe loader lineup, designed to serve contractors, municipalities, and utility crews with a reliable, mid-size machine. Powered by a naturally aspirated 3-cylinder diesel engine and equipped with a mechanical shuttle transmission, the 310A offered straightforward serviceability and solid performance in trenching, grading, and material handling. Its popularity helped establish Deere’s dominance in the backhoe market, with thousands of units sold across North America.
Despite its mechanical simplicity, the 310A’s transmission system includes a lesser-known internal pump that plays a critical role in hydraulic and drive functionality. When this pump fails, the machine may lose mobility entirely—even if the engine runs and the main hydraulic pump has been replaced.
Symptoms of Transmission Pump Failure
A common scenario involves a 310A that starts and runs normally but refuses to move. The engine may idle smoothly, and the hydraulic functions (bucket, boom, stabilizers) may operate with reduced strength or not at all. After replacing the main hydraulic pump, the machine may briefly regain function before losing drive again.
Key symptoms include:

• No forward or reverse movement
  
• Weak or intermittent hydraulic response
  
• No fault codes or warning lights (on analog systems)
  
• Fluid levels appear normal
  
• Transmission engages but fails to transmit torque
  

These signs point toward a failure in the internal transmission charge pump, which supplies fluid to the clutch packs and shuttle system.
Understanding the Transmission Pump System
The 310A uses a shuttle transmission that relies on hydraulic pressure to engage directional clutches. The internal transmission pump—sometimes called the charge pump or shuttle pump—is mounted inside the transmission housing and draws fluid from the reservoir to feed the clutch packs and control valves.
Terminology notes:

• Charge pump: Supplies low-pressure fluid to the transmission control system
  
• Shuttle transmission: Allows directional changes without clutching, using hydraulic clutches
  
• Clutch pack: A set of friction discs and steel plates that engage under hydraulic pressure
  

If the charge pump fails, the clutch packs cannot engage, and the machine will not move. Replacing the main hydraulic pump does not resolve this issue, as the transmission pump operates independently.
Repair Strategy and Machine Splitting
Replacing the internal transmission pump requires splitting the machine at the bellhousing. This is a labor-intensive process that involves:

• Draining all transmission and hydraulic fluid
  
• Removing the loader frame and stabilizers for access
  
• Disconnecting electrical and hydraulic lines
  
• Supporting the engine and transmission with jacks or stands
  
• Separating the engine from the transmission housing
  
• Extracting the failed pump and installing a new or rebuilt unit
  

While challenging, this repair is common among older Deere backhoes and can restore full functionality if performed correctly. Replacement pumps are available from aftermarket suppliers and salvage yards, though part numbers must match the transmission variant.
Field Experience and Practical Advice
A technician in Pennsylvania shared that his 310A stopped moving after a shop replaced the hydraulic pump. The machine ran for a day before losing drive. After consulting with experienced mechanics, he learned about the internal transmission pump and confirmed its failure. Splitting the machine and replacing the pump restored full mobility.
Another operator in Minnesota noted that his 310A had weak hydraulics and intermittent drive. After replacing the charge pump and flushing the system, the machine returned to full strength. He emphasized the importance of inspecting the suction screen and replacing all seals during reassembly.
Preventive Measures and Long-Term Reliability
To avoid transmission pump failure:

• Change transmission fluid every 500 hours or annually
  
• Inspect suction screens and filters during service
  
• Monitor clutch engagement and shuttle response
  
• Avoid overheating the transmission during heavy use
  
• Use high-quality hydraulic fluid with anti-foaming additives
  

Adding a transmission pressure gauge can help detect early signs of pump degradation. If pressure drops below spec during operation, the pump may be wearing out.
Conclusion
The John Deere 310A remains a capable and respected backhoe loader, but its internal transmission pump is a critical component that often goes unnoticed. When drive is lost despite a healthy engine and hydraulic system, the charge pump may be the culprit. By understanding its role, diagnosing symptoms accurately, and performing a careful repair, operators can restore full function and extend the life of this classic machine. Whether digging trenches or loading gravel, the 310A proves that even vintage iron can still deliver when properly maintained.