Diagnosing Right-Side Drive Failure on the Gehl 4835SXT Skid Steer

[MikePhua]

The Gehl 4835SXT and Its Hydraulic Drive System
The Gehl 4835SXT is a mid-frame skid steer loader introduced in the early 2000s, designed for material handling, grading, and light excavation. Powered by a 60-horsepower Deutz diesel engine and weighing approximately 6,000 lbs, the 4835SXT features a hydrostatic drive system that delivers torque to each wheel via independent hydraulic motors. Gehl, founded in 1859, built its reputation on compact equipment, and the 4835 series became a popular choice for contractors and rental fleets across North America.
The SXT variant includes enhanced hydraulic flow and auxiliary circuit support, making it compatible with a wide range of attachments. Its drive system relies on two variable-displacement pumps—one for each side—controlled by mechanical linkages connected to the operator’s hand levers. Each pump feeds a pair of hydraulic motors mounted on the front and rear wheels of its respective side.
Symptoms of Right-Side Drive Loss
When the right side of the machine fails to pull or respond to control input, the issue typically lies within the hydrostatic circuit or mechanical linkage. Common symptoms include:

• No movement on the right side when lever is engaged
  
• Machine spins in circles when attempting to drive forward
  
• Jerky or intermittent motion on one side
  
• Audible whining or cavitation noise from the pump
  
• Hydraulic fluid overheating or foaming
  

A landscaping crew in Ohio reported that their 4835SXT began veering left during transport. After checking tire pressure and linkage movement, they discovered that the right-side drive motor had seized due to internal contamination.
Mechanical Linkage and Control Lever Inspection
The first step is to inspect the mechanical linkage between the control lever and the pump swash plate. Issues may include:

• Broken or disconnected linkage rod
  
• Worn bushings or pivot points
  
• Misaligned lever causing partial pump stroke
  
• Debris obstructing lever travel
  

To diagnose:

• Remove the operator platform and inspect linkage movement
  
• Compare left and right lever response
  
• Manually actuate the pump arm and observe wheel movement
  
• Lubricate pivot points and replace worn components
  

If the linkage is intact and responsive, the problem likely resides within the hydraulic circuit.
Hydraulic Motor and Pump Troubleshooting
Each side of the 4835SXT is powered by a dedicated hydraulic motor. Failure modes include:

• Internal bypass due to worn seals or scoring
  
• Shaft seizure from bearing failure
  
• Contaminated fluid causing spool valve sticking
  
• Cavitation from air ingress or low fluid level
  

To test:

• Swap hydraulic hoses between left and right motors to isolate the issue
  
• Use a flow meter to measure output from the pump
  
• Inspect motor case drain for excessive flow (indicating internal leakage)
  
• Check for metal shavings or discoloration in the fluid
  

If the motor is confirmed faulty, replacement or rebuild is necessary. Use OEM-grade seals and torque specs during reassembly.
Pump Output and System Pressure Checks
The hydrostatic pump may fail to deliver adequate pressure due to:

• Worn swash plate or pistons
  
• Cracked housing or internal scoring
  
• Faulty charge pump reducing inlet pressure
  
• Relief valve stuck open
  

Recommended steps:

• Install pressure gauges on pump output ports
  
• Compare left and right side readings under load
  
• Inspect charge pump filter and suction screen
  
• Replace relief valve if pressure is below spec
  

A technician in Alberta rebuilt the right-side pump on a 4835SXT after discovering that the swash plate had worn unevenly, causing reduced stroke and poor motor engagement.
Hydraulic Fluid and Filter Maintenance
Contaminated or degraded fluid can cause widespread drive issues. Best practices include:

• Replace hydraulic fluid every 1,000 hours or annually
  
• Use ISO 46 or manufacturer-approved fluid
  
• Replace filters every 500 hours
  
• Flush system after motor or pump failure
  
• Inspect reservoir for sludge or water contamination
  

Install magnetic plugs and sight gauges to monitor fluid condition. Some operators retrofit inline filters with pressure sensors for early warning.
Preventive Measures and Long-Term Care
To maintain drive system health:

• Grease control linkages weekly
  
• Inspect hoses and fittings monthly
  
• Monitor fluid temperature during operation
  
• Avoid abrupt directional changes at high RPM
  
• Store machine under cover to prevent moisture ingress
  

Operators should report any change in drive feel immediately. Early intervention prevents cascading failures across the hydraulic system.
Conclusion
Loss of right-side drive in the Gehl 4835SXT is often caused by mechanical linkage failure, hydraulic motor wear, or pump degradation. With methodical inspection, pressure testing, and fluid analysis, the issue can be resolved and full mobility restored. These machines, though aging, remain reliable when maintained with care—proving that hydrostatic drive systems, while complex, are serviceable with the right approach.