2025 International LT Transmission Fluid & Service

Quick Answer

• Transmission Make/Model: Eaton Endurant XD / XD Pro Series (various models available depending on configuration)
• OEM Fluid Spec: Eaton PS-386 extended drain fluid (or equivalent meeting Eaton's PS-386 specification). Always verify the specific PS-386 revision or newer Eaton specification for your exact transmission with the dealer or service manual.
• Drain & Fill Capacity: Varies significantly by specific Endurant XD/XD Pro model due to cooler size and line length. Typically ranges from 16 to 22 quarts (15 to 21 liters). Always consult your truck's owner’s manual or Eaton service literature for the precise capacity.
• Full Overhaul Capacity: Varies. Consult Eaton service literature for specific model.
• Filter OEM Part Number: Verify with Eaton dealer or service manual. Eaton Endurant transmissions generally use an internal filtration system, and external serviceable filters may vary or be integrated. Specific part numbers are dependent on the exact transmission model and build.
• Recommended Service Interval:
  • Normal Duty: Up to 500,000 miles (800,000 km) or 5 years, whichever comes first, when using Eaton PS-386 fluid and proper oil analysis.
  • Severe Duty/Towing: Up to 250,000 miles (400,000 km) or 2.5 years, whichever comes first, when using Eaton PS-386 fluid and proper oil analysis. Oil analysis is critical for extending intervals in severe applications.

Fluid Type Explained

The 2025 International LT, especially when equipped with the increasingly popular Eaton Endurant XD or XD Pro automated manual transmissions (AMTs), requires a high-performance, purpose-designed transmission fluid. For these transmissions, Eaton specifies their proprietary Eaton PS-386 extended drain fluid. This specification is crucial because standard, generic transmission fluids do not meet the stringent demands of these advanced transmissions.

Eaton PS-386 fluid is engineered to provide superior protection for gears, bearings, and synchronizers, while maintaining optimal viscosity across a wide range of operating temperatures. It offers excellent thermal stability, shear stability, and oxidation resistance, which are all vital for the extended service intervals and heavy-duty applications that the International LT is designed for. Using a fluid that does not meet or exceed the PS-386 specification can lead to premature wear, reduced fuel efficiency, and potential transmission failure, often voiding your warranty.

Always verify the exact Eaton fluid specification (e.g., a specific revision of PS-386 or a newer Eaton spec) recommended for your specific Endurant transmission model with your International dealer or the truck's service manual. Aftermarket fluids claiming to meet PS-386 should be carefully vetted to ensure they are fully compliant and approved by Eaton for use in your transmission.

Service Procedure

Servicing an Eaton Endurant transmission fluid and filter is a critical maintenance task.

Drain & Fill:

1. Preparation: Ensure the truck is on level ground, engine is off, and the transmission is at operating temperature for best fluid drainage. Engage parking brake and chock wheels. Gather necessary tools, a large drain pan, and new Eaton PS-386 spec fluid.
2. Locate Drain Plug: The drain plug is typically located at the bottom of the transmission pan. It may require a specific wrench size.
3. Drain Fluid: Place your drain pan under the plug and carefully remove it. Allow all the old fluid to drain completely. This can take some time. Inspect the fluid for any unusual debris or metallic particles, which could indicate internal wear.
4. Filter Replacement: Eaton Endurant transmissions often have internal filters designed for long life, but some configurations might have serviceable external filters or strainers. Consult your service manual for the exact filter location and replacement procedure. If an internal filter is present, it's generally not a routine service item during a simple drain and fill; full overhaul scenarios typically address internal filters.
5. Reinstall Drain Plug: Once drained, clean the drain plug and surrounding area. Reinstall the drain plug with a new washer (if specified) and torque to the manufacturer's specifications.
6. Refill: Locate the fill plug (usually on the side of the transmission). Using a hand pump or fluid transfer system, begin adding the new Eaton PS-386 fluid. Fill until fluid begins to seep out of the fill hole. Note that the Endurant XD/XD Pro transmissions are sensitive to overfilling or underfilling. Some models have sight glasses or dipsticks, while others require specific fill procedures based on temperature. Always refer to your truck's owner's manual or Eaton service manual for the precise refill procedure and capacity. Start the engine, cycle through gears, then recheck fluid level if specified.

Full Exchange (Fluid Flush):

A full fluid exchange or flush is generally not recommended for Eaton Endurant transmissions using external pressure flushing equipment due to the complexity of the internal hydraulic circuits and potential for damage or incorrect fluid levels. A drain and fill, performed correctly and at the recommended intervals with proper oil analysis, is usually sufficient. If a complete fluid change is deemed necessary (e.g., after an internal repair), it typically involves multiple drain and fill cycles or specialized service procedures performed by trained technicians.

Service Interval

The service interval for your 2025 International LT with an Eaton Endurant transmission is primarily dictated by the type of duty cycle and the use of Eaton PS-386 extended drain fluid. Oil analysis is highly recommended and can be crucial for safely extending these intervals.

• Normal Duty: For typical highway operations, light loads, and minimal idling, Eaton recommends a service interval of up to 500,000 miles (800,000 km) or 5 years, whichever comes first. This is contingent on using the specified Eaton PS-386 fluid and adhering to manufacturer guidelines.
• Severe Duty/Towing: For applications involving heavy loads, frequent stop-and-go driving, excessive idling, steep grades, or consistent towing, the service interval is reduced to approximately 250,000 miles (400,000 km) or 2.5 years, whichever comes first. In these conditions, the transmission fluid experiences higher temperatures and increased stress, leading to faster degradation.

Regular oil analysis (sampling the transmission fluid at recommended intervals) can provide valuable insights into the fluid's condition and help determine if the service interval can be safely extended or if an earlier change is warranted. Conditions such as contamination by coolant, fuel, or excessive wear metals will necessitate an earlier fluid change.

Common Transmission Problems (Eaton Endurant XD / XD Pro Generation)

While the Eaton Endurant XD/XD Pro transmissions are generally robust and reliable, like any complex mechanical system, they can experience specific issues. For the 2025 International LT, common concerns for this generation of AMT include:

• Sensor Malfunctions: Faulty speed sensors, range sensors, or temperature sensors can lead to erratic shifting,