Case 1845C Right-Side Drive Failure: Diagnosis, Repair, and Lessons from the Field

[MikePhua]

Understanding the Drive System
The Case 1845C skid steer uses a hydrostatic drive system with two independent hydraulic motors—one for each side. These motors receive pressurized fluid from a tandem hydraulic pump, allowing precise control of movement. When one side fails to drive properly, the issue may stem from mechanical wear, hydraulic imbalance, or control linkage misalignment.
Terminology Notes

• Hydrostatic Drive: A system using hydraulic fluid to transmit power from the pump to the drive motors.
  
• Tandem Pump: A dual-section hydraulic pump supplying fluid to both drive motors.
  
• Drive Motor: Hydraulic motor responsible for propelling each side of the skid steer.
  
• Chain Case: Enclosure housing the drive chains and sprockets.
  
• Tow Valve: A valve that allows the machine to be moved manually without engine power.
  
• Rotating Group: Internal motor components including pistons and cylinder block, critical for hydraulic function.
  

Initial Symptoms and Inspection
Operators reported the right side of the machine pulling slower than the left, especially under load or on inclines. Upon inspection:

• Left chain case oil appeared clean and milky white
  
• Right chain case oil was rusty and contaminated
  
• Chains and sprockets were intact
  
• No visible mechanical damage
  

This contrast suggested water intrusion or seal failure on the right side, potentially affecting bearing integrity and hydraulic performance.
Common Causes of One-Sided Drive Failure

• Contaminated Chain Case Oil
  Water ingress through cracked chain case covers or failed seals can degrade lubrication and cause rust.
  
• Worn Drive Motor
  Hydraulic shops confirmed that the rotating group in the right-side motor was worn out, reducing torque output.
  
• Pump Imbalance or Failure
  Even after motor replacement, the issue persisted, pointing to a possible fault in the tandem pump.
  
• Linkage Misalignment
  Uneven control lever travel or worn joints can cause unequal fluid flow, leading to directional imbalance.
  
• Parking Brake Interference
  Loose or misadjusted brake cables may engage partially, restricting movement and risking chain damage.
  

Field Repairs and Lessons Learned

• Motor Replacement
  A new drive motor was installed, but performance remained poor. This highlighted the importance of testing the pump before replacing components.
  
• Pump Diagnosis
  Hydraulic shops recommended replacing the tandem pump rather than rebuilding due to cost and part availability. A remanufactured unit was sourced for $2,100.
  
• System Flushing
  Contaminated oil was drained, chain cases flushed, and filters replaced. Multiple oil changes were performed to remove residual debris.
  
• Control Linkage Adjustment
  Linkages were inspected and adjusted to ensure equal travel and responsiveness on both sides.
  
• Orifice Cleaning
  A technician suggested removing and cleaning the restriction orifice on the pump to eliminate potential blockages affecting flow.
  

Real-World Anecdotes and Operator Wisdom

• A mechanic shared that brittle seals often result from overheating due to debris buildup around the drive system. Regular cleaning prevents insulation and heat retention.
  
• Another operator discovered that switching hydraulic lines between sides helped isolate pump issues. When the problem moved with the lines, the pump was confirmed as the culprit.
  
• A retired quarry mechanic emphasized cutting open used filters to inspect for metal shavings or sludge—a cost-effective way to monitor system health.
  
• In one case, a faulty tow valve setting caused drive loss. Resetting the valve restored function without replacing parts.
  

Preventive Maintenance Tips

• Inspect chain case covers for cracks and seal them with RTV to prevent water ingress
  
• Grease axle shaft fittings regularly to maintain bearing health
  
• Check and adjust chain tension equally on both sides
  
• Monitor hydraulic fluid quality and change filters proactively
  
• Test drive motor and pump pressures before replacing components
  

Conclusion: Diagnosing Beyond the Obvious
The Case 1845C’s right-side drive failure illustrates the layered complexity of hydraulic systems. While a worn motor may seem the obvious culprit, deeper issues like pump imbalance, contaminated oil, or control linkage misalignment often lurk beneath. Field experience, methodical testing, and preventive care are the keys to restoring performance and avoiding costly missteps. As one veteran mechanic put it, “Don’t just fix what’s broken—understand why it broke.”