John Deere 490E Track Loader: Tackling Oil Leaks Around the Ring Gear

[MikePhua]

A persistent oil leak around the swing area or ring gear of a 490E can be more than just an annoyance—it’s a warning sign. Understanding the root causes and addressing them precisely can save time, money, and frustration.
Why Oil Might Be Seeping Around the Ring Gear

• Water Contamination in Grease Reservoir
  • If moisture enters the swing gearbox or area near the ring gear, the grease becomes diluted (“watered down”), drastically reducing its lubrication properties and allowing fluid to escape freely.
    
• Worn or Incorrect Seals & O-Rings
  • Even when O-rings appear intact, material fatigue, misalignment, or age-related hardening can still cause slow, steady leaks.
    
• Rotating Manifold (Rotator) Wear
  • The rotator responsible for routing hydraulic fluid to track motors may develop grooves or wear. When this happens, fluid can seep—even if drives seem functional.
    
• Brake Line or Fitting Issues
  • Leaks from brake system hoses or fittings near the swing pin area, though less common, can lead to fluid accumulation and make it seem like ring gear leakage.
    

True Story from the Yard
A mid-career heavy machinery tech once diagnosed a 490E that refused to hold pressure at the turntable. After chasing seals and flushing lines, the culprit turned out to be water-diluted grease—picked up during a rainy week of power-washing. Replacing the grease and sealing the drain port stopped the leak entirely.
Troubleshooting Checklist

• Drain residual fluid from the swing gearbox and inspect for hazy, watered-down grease.
  
• Replace all suspect O-rings and seals—even those that look visually okay.
  
• Inspect the rotator surface for grooves; if surfaced, consider a remanufactured replacement.
  
• Look for brake fluid or hydraulic fluid pooling near fittings on the swing structure.
  

Recommended Actions and Prevention

• Flush and refill the swing gearbox with fresh, heavy-duty gear grease—ensure it’s rated for water resistance.
  
• Replace all seals systematically, not just the most visible ones.
  
• If wear is present, install a remanufactured rotator to restore proper manifold sealing.
  
• Apply corrosion-resistant coatings or protective covers around exposed seals to prevent wash-through.
  
• Schedule periodic checks after washing or working in wet environments to catch early signs of moisture intrusion.
  

Technical Terms Glossary

• Swing Gearbox: The assembly housing the ring and pinion gears allowing upper structure rotation.
  
• Rotator (Rotary Manifold): A rotating hydraulic distribution unit feeding drive circuits while the upper structure pivots.
  
• Grease Water Contamination: When moisture mixes with gear grease, reducing lubrication and promoting leakage.
  
• O-Ring / Seal: Elastomeric rings designed to block fluid migration between mating surfaces.
  

Quick Reference Summary

• Likely Causes
  • Water-diluted grease
    
  • Degraded seals or O-rings
    
  • Rotator wear or grooves
    
  • Nearby brake/hydraulic fitting leaks
    
• Steps to Diagnose
  • Inspect grease consistency
    
  • Replace seals comprehensively
    
  • Examine rotator surface integrity
    
  • Check adjacent component fittings
    
• Preventive Tips
  • Use water-resistant grease
    
  • Apply protective measures during cleaning
    
  • Follow up with regular leak inspections
    

With careful inspection, proper replacement of seals, and attention to how the rotator behaves, it’s entirely possible to eliminate persistent ring gear leaks—and keep the 490E turning smoothly for years to come.