Servicing the Gearcase and Chain Case on a John Deere 6675 Skid Steer

[MikePhua]

Legacy of the John Deere 6675
The John Deere 6675 skid steer loader was introduced in the mid-1990s as part of Deere’s push into compact construction equipment. Built during a period when mechanical simplicity and ruggedness were prioritized, the 6675 featured a robust hydrostatic drive system, mechanical controls, and a reliable diesel engine. With a rated operating capacity of approximately 1,750 lbs and a tipping load near 3,500 lbs, it became a favorite among contractors, landscapers, and farmers. Though production ceased decades ago, many units remain in service due to their ease of maintenance and parts availability.
Gearcase and Final Drive Chain Service
One of the most critical maintenance tasks on the 6675 involves servicing the gearcase and final drive chains. These components transfer power from the hydrostatic wheel motors to the drive wheels through a chain-and-sprocket system housed in sealed compartments.
When replacing a hydro wheel motor or performing a full teardown, it’s essential to refill the gearcase and chain case with the correct lubricants:

• Gearcase: Use 80W-90 gear oil, a high-viscosity lubricant designed to protect gears under heavy load and prevent metal-to-metal contact.
  
• Chain Case and Hydraulic Compartments: Use 10W-30 engine oil, which provides adequate lubrication for chains and hydraulic components while maintaining flow characteristics in cold starts.
  

Terminology Clarification

• Hydro Wheel Motor: A hydraulic motor mounted at each wheel that drives the skid steer via fluid pressure.
  
• Final Drive Chain: A heavy-duty roller chain that connects the motor’s output to the wheel hub.
  
• Gearcase: A sealed housing containing gears and oil, responsible for torque transfer and load distribution.
  
• Chain Case: The compartment where drive chains operate, often sharing space with hydraulic fluid or engine oil.
  

Best Practices for Reassembly and Lubrication
After removing the gearcase and chains, follow these steps for reliable reassembly:

• Clean all mating surfaces and remove old gasket material.
  
• Inspect sprockets and chains for wear, elongation, or broken links.
  
• Replace seals and gaskets to prevent future leaks.
  
• Fill gearcase slowly to avoid air pockets; check oil level after running the machine briefly.
  
• Use a torque wrench to tighten bolts to manufacturer specifications.
  

One technician reported that after replacing a hydro motor and refilling the gearcase with 80W-90, the machine ran smoother and quieter, with improved traction and reduced vibration. He also noted that using synthetic gear oil extended service intervals by nearly 30%.
Preventive Maintenance Tips
To keep the 6675 running reliably:

• Check oil levels monthly in both gearcase and chain case.
  
• Grease all pivot points daily, especially in dusty or wet conditions.
  
• Inspect drive chains every 500 hours for tension and wear.
  
• Flush hydraulic fluid every 1,000 hours or annually, whichever comes first.
  

Conclusion
Servicing the gearcase and chain case on a John Deere 6675 is a straightforward but essential task that ensures long-term performance and reliability. Using the correct lubricants—80W-90 for gears and 10W-30 for chains and hydraulics—prevents premature wear and supports smooth operation. With proper care, this classic skid steer can continue working hard for decades, proving that mechanical simplicity still has a place in modern job sites.