How Much Oil Should Be Used for Axle Chain Cases in Case Skid Steers

[MikePhua]

The Case 1840 and Its Chain Drive Architecture
The Case 1840 skid steer loader was introduced in the early 1990s as part of Case Construction Equipment’s compact equipment lineup. With a rated operating capacity of approximately 1,400 lbs and powered by a 51-horsepower diesel engine, the 1840 quickly became a favorite among contractors, farmers, and rental fleets. Its mechanical simplicity, chain-driven axles, and robust frame contributed to over 60,000 units sold globally before production transitioned to newer models like the 1845C.
Unlike hydrostatic drive systems that use planetary final drives, the 1840 relies on a chain case system to transmit torque from the hydraulic motors to the wheels. Each side of the machine houses a pair of drive chains immersed in oil, which lubricates the links and sprockets while also helping to dissipate heat generated during operation.
Recommended Oil Type and Capacity
For chain case lubrication, Case recommends SAE 30-weight non-detergent oil. This viscosity provides adequate film strength for chain protection without foaming or excessive drag. Detergent oils are discouraged because they can suspend contaminants and moisture, leading to emulsification and reduced lubrication performance.
Typical oil capacities are:

• Case 1840: Approximately 6 quarts per side
  
• Case 1845C: Approximately 5 quarts per side
  

These figures may vary slightly depending on chain wear, case geometry, and whether the machine is parked level during filling. The goal is to maintain enough oil for the chain to dip and carry lubrication around the sprockets without overfilling, which can cause leaks or aeration.
Drain and Refill Procedure
Before refilling, it’s essential to drain and inspect the chain case thoroughly. Water intrusion, bearing debris, and gasket remnants are common in older machines. A proper service routine includes:

• Removing the drain plug and allowing full oil evacuation
  
• Rinsing the case with clean oil or kerosene to flush contaminants
  
• Using a flashlight to inspect for broken links, loose fasteners, or seal damage
  
• Replacing the drain plug with a new gasket or sealant
  
• Refilling with SAE 30 oil to the recommended level
  

Some operators use a dipstick or sight plug to verify oil level, but in many models, the fill port itself serves as a level indicator—once oil begins to seep from the port, the case is full.
Field Anecdote from South Texas
A retired hotrod builder in Falfurrias, Texas restored a Case 1840 and noticed erratic drive performance. After disassembling the chain case, he found water-contaminated oil and fragments of a failed bearing. After flushing the case and refilling with 6 quarts of SAE 30 oil per side, the machine regained smooth operation. He now checks chain case oil monthly and uses a moisture-absorbing breather cap to prevent condensation.
Preventive Maintenance and Long-Term Reliability
To extend the life of the chain drive system:

• Change chain case oil every 500 hours or annually
  
• Inspect for leaks around axle seals and case gaskets
  
• Avoid pressure washing near breather caps or fill ports
  
• Monitor for unusual noises or jerky movement during travel
  
• Use magnetic drain plugs to capture wear particles
  

In humid climates or machines stored outdoors, condensation can accumulate inside the chain case. Installing desiccant breathers or vent tubes with check valves can reduce moisture ingress.
Industry Trends and Design Evolution
Modern skid steers have largely transitioned to planetary final drives and enclosed hydrostatic systems. While these offer improved torque and reduced maintenance, they are more complex and costly to repair. The chain drive system in the Case 1840 remains popular among owner-operators who value mechanical simplicity and field serviceability.
A 2023 survey of independent equipment shops in the Midwest found that chain-driven skid steers accounted for 18% of active service calls, with chain case oil changes being the most common maintenance task. Technicians emphasized the importance of using correct oil type and volume to prevent premature chain wear.
Conclusion
Maintaining proper oil levels in the axle chain cases of Case skid steers like the 1840 is essential for drivetrain longevity and performance. Using SAE 30 non-detergent oil and adhering to a 5–6 quart fill guideline ensures adequate lubrication without overfilling. With regular inspection and preventive care, the chain drive system can deliver thousands of hours of reliable service, preserving the legacy of one of Case’s most enduring compact machines.