John Deere 310A Backhoe Lost Steering — What Went Wrong and How to Fix It

[MikePhua]

Background on the 310A Steer System
The John Deere 310A is a classic backhoe loader built in the 1970s–1980s. Its hydraulic system is a closed‑center, constant‑pressure design, meaning the hydraulic fluid is stored within the transmission case itself, which doubles as the reservoir.  The steering is powered via a priority system: when the operator turns the steering wheel, the hydraulic flow is routed to a steering valve, then on to a steering cylinder that turns the front wheels.

Symptom: Sudden Loss of Steering
One owner reported that while operating the 310A, the steering suddenly failed: “wheels went to the right and that was that.”  Despite having fluid in both steering lines, there was no resistance when the steering wheel was turned — the steering wheel “turns, and turns, and turns.”

Diagnosis by the Community

• A seasoned member suggested testing the cylinder seal: remove the rod-end hose from the steering cylinder, run the engine, and try steering. If oil gushes out the rod end, it’s a strong sign the piston seal inside the steering cylinder is blown.
  
• When the owner followed this advice, they discovered that the nut on the steering ram had come off completely, and the threads were stripped — meaning the piston was no longer secured and thus couldn’t steer properly.
  

Contributing Factors
From similar cases and historical mechanics’ input, a few common root causes for steering failure on older 310A backhoes include:

• Worn or missing steering gear internals: Some 310/410 models had worn or missing ball bearings inside the steering gearbox, compromising the worm-gear mechanism.
  
• Air in the hydraulic system (aeration): Low fluid levels or a leaking suction line can introduce air, leading to weak or intermittent steering.
  
• Priority or check valve problems: These valves help route flow to steering or implement circuits as needed. If they leak internally or the spring fails, steering pressure can be lost.
  
• Pump or coupling wear: Some reports suggest that coupling spline wear or failing pump parts can starve the steering circuit.
  

Repair Steps & Recommendations

1. Inspect the Steering Cylinder
   • Remove the rod-end hose, run the engine, and try to steer. If fluid comes out freely, the piston seal is likely damaged.
     
   • Disassemble the cylinder, inspect the ram threads, and check for a missing or loose nut. Replace or resecure as needed.
     
2. Check Hydraulic Fluid Level & Quality
   • Verify that the hydraulic/transmission fluid is at the correct level. Low fluid can lead to aeration and loss of steering pressure.
     
   • If the fluid level is okay but problems persist, consider checking the internal suction lines or charge pump for leaks or wear.
     
3. Inspect Priority Valve / Steering Valve
   • Use a service manual to locate and test the priority or check valve in the steering system. John Deere’s service manual provides procedures for inspecting valve spools, springs, and internal flow paths.
     
   • If the valve is stuck or the spring is weak, rebuild or replace the valve components.
     
4. Evaluate Steering Gearbox
   • If there is play in the steering worm gear or missing bearings, remove the gearbox cover and examine internal parts.
     
   • Replace worn bearings, shims, or worm gear as needed.
     
5. Bleed the System
   • After any repair, bleed air from the hydraulic system by operating the steering at idle and working it through its stroke slowly.
     
   • Monitor fluid level during and after bleeding; you may need to top off due to fluid lost during the purge.
     

Lessons Learned & Preventive Advice

• Thread Torque Matters: Loose nuts on steering rams can be a catastrophic failure point. Always torque ram fasteners to spec and recheck after maintenance.
  
• Routine Inspection: Periodically inspect steering hoses for leaks, cylinder mounting, and linkage integrity.
  
• Use Proper Fluid: Use the correct hydraulic/transmission fluid as specified by John Deere to reduce risk of aeration or priority-valve malfunction.
  
• Keep a Manual Handy: Having the John Deere 310A Service Manual is crucial for diagnosing hydraulic and steering issues.
  

Conclusion
In the case of the 310A backhoe, the root cause of the lost steering wasn’t a mysterious hydraulic failure—but a mechanical failure: a loose ram nut. Combined with community troubleshooting and past experience, key maintenance steps can prevent and repair similar failures. Ensuring tight fasteners, clean hydraulic circuits, and well-functioning priority valves will help restore reliable steering and prevent future loss of control.