2018 International LT: Transmission & Axle Ratios

Transmission Gear Ratios

The 2018 International LT was available with a wide array of transmissions from Eaton Fuller, Tremec, and Allison. Each is designed to meet specific demands, from long-haul fuel efficiency to heavy-haul durability.

Eaton Fuller Advantage Series (Automated)

These 10-speed automated manuals are designed for optimal fuel economy in over-the-road applications.

Eaton Fuller RTLO-Series (Manual)

These heavy-duty 13- and 18-speed manual transmissions are legendary for their durability and are favored for vocational and heavy-haul applications.

13-Speed (RTLO-16913A)

18-Speed (RTLO-18918B)

Allison TC-10 (Automatic)

This 10-speed fully automatic transmission combines a torque converter with a twin countershaft gearbox, offering excellent performance and driver comfort.

Available Axle Ratios

Axle ratios on the International LT are matched to the engine, transmission, and intended application (line haul, heavy haul, etc.). Ratios are offered from manufacturers like Meritor and Dana.

How to Identify Your Axle Ratio

Unlike passenger cars, commercial trucks provide this information in a few standardized ways.

• VIN Decoder: The most reliable method is to use a commercial truck VIN decoder. The VIN contains specific details about how the truck was configured from the factory, including the exact axle model and ratio.
• Axle Tag: Look for a metal tag bolted to the differential housing of the drive axles. This tag is stamped with information from the axle manufacturer (e.g., Meritor, Dana) and will include the precise ratio (e.g., "3.36") and model number.
• Line Setting Ticket: Sometimes called a build sheet, this document is the complete specification list for the truck when it was ordered. It will list the axle models, ratios, and every other component. This may be found in a pouch with the owner's manuals or can be requested from an International dealer with the VIN.

Towing vs. MPG Impact

In a Class 8 truck like the International LT, the relationship between axle ratio, fuel economy, and performance is critical for profitability.

• Numerically Lower Ratios (e.g., 2.26, 2.47): These are known as "fast" gears. They cause the driveshaft to turn fewer times for each rotation of the wheel. This keeps engine RPMs very low at highway speeds (a practice called "downspeeding"), which significantly reduces fuel consumption. These ratios are ideal for long-haul carriers traveling on flat terrain where maximizing MPG is the top priority.

• Numerically Higher Ratios (e.g., 3.36, 3.55): These are "slow" gears. They multiply the engine's torque more effectively, making it easier to get a heavy load moving from a standstill and to pull grades without constant downshifting. This increased pulling power comes at the cost of higher engine RPMs at cruising speed, which leads to lower fuel economy. These ratios are essential for heavy-haul, vocational, or regional applications with frequent stops and hilly terrain.

Common Issues

While the driveline components on the International LT are built to be robust, they are subject to immense stress and can exhibit wear over hundreds of thousands of miles.

• Pinion and Carrier Bearing Wear: A constant, speed-sensitive humming or whining from the drive axles is a classic symptom of worn pinion or carrier bearings. The sound may change pitch under acceleration or deceleration. Addressing this early is key to avoiding a catastrophic failure of the gear set.
• Ring & Pinion Gear Whine: If the gears themselves are worn or were not set up with the correct backlash, they can produce a whining sound. This is distinct from a bearing whine and often indicates the gear set is approaching the end of its life.
• Inter-Axle Differential Failure: On tandem-axle trucks, the power divider (or inter-axle differential) allows for speed differences between the forward and rear axles when turning. Failure in this unit can cause binding, grinding noises, or a complete loss of power.

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