2024 International MV Transmission Fluid & Service

Quick Answer

• Transmission Make/Model: Allison 2500 HS (common in MV series, verify specific model with your vehicle)
• OEM Fluid Spec: Allison TES 668™ (recommended for Allison 1000/2000/2500 series transmissions)
• Drain & Fill Capacity: Approximately 16-19 quarts (varies based on pan size and cooler lines; always check dipstick)
• Full Overhaul Capacity: Approximately 29-32 quarts (verify with service manual)
• Filter OEM Part Number: Internal main filter: Allison 29545778 (spin-on filter may also be present depending on configuration like Allison 29548988; verify with dealer or service manual based on your specific transmission and pan type)
• Recommended Service Interval (Normal Duty): 48 months or 160,000 miles, whichever comes first.
• Recommended Service Interval (Severe Duty / Towing): 24 months or 80,000 miles, whichever comes first.

Fluid Type Explained

The 2024 International MV series frequently utilizes the robust Allison 2500 HS (Highway Series) automatic transmission, known for its durability and performance in medium-duty applications. For these transmissions, the exclusive recommendation is Allison TES 668™ approved fluid. This is a significant advancement engineered to provide superior protection and extended drain intervals compared to older specifications like TES 295.

Allison TES 668™ fluids are designed with enhanced additive packages that offer improved thermal stability, oxidation resistance, and shear stability. These properties are crucial for maintaining optimal transmission performance and longevity, especially given the demanding operational conditions often faced by International MV trucks, such as urban delivery, vocational use, and regional hauling. Using a fluid that meets the TES 668™ specification ensures your transmission operates at its peak, with reduced wear and tear on internal components.

While some older Allison transmissions might have used TES 295, it'simperative to use TES 668™ for the 2024 models where specified, or when upgrading from TES 295 to take advantage of the superior performance and extended drain intervals. Always verify the exact fluid specification in your vehicle's owner's manual or service information, as specific configurations can vary.

Service Procedure

Servicing your Allison transmission on a 2024 International MV is a critical maintenance item. There are typically two main approaches: a drain and fill, or a full fluid exchange.

Drain & Fill: This involves draining the fluid from the transmission pan, replacing the internal filter(s), and refilling with new fluid. This method replaces only a portion of the total transmission fluid, leaving some of the old fluid in the torque converter and cooler lines. For a typical drain and fill on an Allison 2500 HS, you can expect to need approximately 16-19 quarts. Always use the dipstick to verify the correct fluid level after the service, running the engine and shifting through the gears to circulate the fluid.

Full Fluid Exchange: A full fluid exchange (or flush) is a more comprehensive service where specialized equipment is used to replace nearly all of the old transmission fluid with new. This method ensures that contaminated fluid from the torque converter and cooler is also removed. This approach often requires the full overhaul capacity of fluid, which can be around 29-32 quarts for an Allison 2500 HS. While a full exchange offers maximum benefit, it should always be performed by a qualified technician using the correct equipment and procedures to avoid damage. Allison generally recommends a double drain and fill for routine maintenance rather than a pressurized flush, consult your Allison service manual or dealer for specifics.

Regardless of the method, always ensure the transmission is at the correct operating temperature for an accurate fluid level check. Overfilling or underfilling can lead to transmission problems.

Service Interval

The service intervals for your 2024 International MV's Allison transmission are crucial for its longevity and performance, and they vary significantly based on operating conditions.

Normal Duty: For vehicles operating under typical conditions, such as light hauling, highway driving, and minimal idling, Allison recommends a fluid and filter change every 48 months or 160,000 miles, whichever comes first. This interval assumes the use of Allison TES 668™ approved fluids.

Severe Duty / Towing: If your International MV is subjected to more strenuous conditions, such as heavy hauling, frequent towing, vocational use with PTO operation, extensive idling, or operation in extremely hot or cold climates, the service interval should be significantly reduced. For these severe duty applications, it's recommended to perform a fluid and filter change every 24 months or 80,000 miles, whichever comes first. This more frequent servicing helps ensure that the fluid's protective properties remain optimal under the increased stress.

Always consult your owner's manual and the Allison Operation and Maintenance Manual for the most accurate and up-to-date service schedule for your specific vehicle and transmission configuration. Regular fluid analysis can also help determine if fluid life is being maximized or if more frequent changes are necessary.

Common Transmission Problems

While the Allison 2500 HS transmission in the 2024 International MV is renowned for its reliability, like any mechanical component, it can experience issues. Understanding common problems can help with early diagnosis and prevention.

• Delayed Engagement or No Engagement: This can manifest as a noticeable delay when shifting into drive or reverse, or a complete lack of engagement. It could indicate low fluid level, old/degraded fluid, a faulty solenoid, or internal wear.
• Rough Shifting or Harsh Engagements: Unusually hard shifts, clunking noises, or sudden jerks between gears can point to issues with fluid pressure, worn clutches, a malfunctioning valve body, or sensor problems.
• Slipping: The engine revs but the truck doesn't accelerate as it should, or it feels like the transmission is struggling to maintain a gear. This is a classic sign of worn clutch packs or low fluid pressure.
• Overheating: The transmission fluid temperature gauge reading high can be caused by low fluid, heavy loads, restricted cooler lines, a failing torque converter, or internal transmission issues. Overheating can rapidly degrade fluid and damage internal components.
• Fluid Leaks: Any signs of red fluid underneath the truck indicate a leak. Common leak points include the pan gasket, output shafts, cooler lines, or sensor seals. Leaks can lead to low fluid levels and subsequent damage.
• Check Transmission Light / Diagnostic Trouble Codes (DTCs): Modern Allison transmissions are highly sophisticated and will often illuminate a check transmission light or stored DTCs in the event of an electrical or functional fault. Professional diagnostic scanning is essential to interpret these codes and pinpoint the exact issue.

Regular maintenance, including using the correct Allison TES 668™ fluid and adhering to service intervals, is the best defense against these common problems, maximizing the lifespan and performance of your transmission.

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