2024 International LT Transmission & Axle Gear Ratios

Transmission gear ratios

The 2024 International LT offers a range of robust transmission options designed to meet various operational demands, from long-haul efficiency to vocational heavy hauling. The specific internal gear ratios for each transmission are critical for understanding the truck's performance characteristics.

Eaton Fuller Advantage 10-Speed Automated Manual Transmission (AMT)

Eaton Fuller Advantage 12-Speed Automated Manual Transmission (AMT)

Allison 4000 Series Automatic Transmission (typical ratios, may vary by specific model)

Available axle ratios

Axle ratios are crucial for optimizing the 2024 International LT for specific applications, balancing fuel economy with pulling power. The availability of certain ratios will depend on the engine, transmission, and specific truck configuration.

Note: Axle codes (RPO) are for illustrative purposes and actual codes should be verified on your specific vehicle's RPO sticker.

How to identify your axle ratio

Identifying your International LT's axle ratio is straightforward and can be done using a couple of methods:

• Door-Jamb RPO Sticker (GM-style for Navistar): For International trucks, look for a sticker typically located on the driver's side door jamb or inside the glove compartment. This sticker will list numerous three-digit "RPO" (Regular Production Option) codes. You'll need to cross-reference these codes with an International RPO decoder or consult a dealer parts department to find the specific axle ratio code. Common codes for axle ratios often start with "DM", "DB", "DD", or "DE" followed by numbers and letters. For example, a code like "DM5" might indicate a 2.85 ratio, though these codes can vary by model year and specific build.

• Axle Tag: Many heavy-duty axles include a metal tag bolted to one of the differential cover bolts or stamped into the axle housing itself. This tag contains vital information, including the gear ratio, the manufacturer, and sometimes the build date. The ratio will typically be stamped as a two-digit number followed by a two-digit number (e.g., "308" for 3.08, or "355" for 3.55). Ensure the vehicle is safely supported and wheels chocked before attempting to visually inspect the axle tag.

• VIN Decoder: While not as common for directly specifying the axle ratio, a comprehensive VIN decoder or consulting with an International dealer using your full VIN can often provide a detailed build sheet that includes the installed axle ratio.

Towing vs MPG impact

The choice of axle ratio has a profound impact on the performance and economy of your 2024 International LT:

• Numerically Lower Ratio (e.g., 2.64, 2.85, 3.08): These "taller" gears result in lower engine RPMs at highway speeds. This translates directly to better fuel economy, as the engine does not have to work as hard to maintain speed. However, with a numerically lower ratio, the truck will have less torque multiplication at the wheels, meaning reduced pulling power and slower acceleration, especially when heavily loaded or climbing grades. These ratios are ideal for long-haul applications where fuel efficiency is paramount and the truck operates primarily on relatively flat terrain.

• Numerically Higher Ratio (e.g., 3.42, 3.58, 3.73, 3.90): These "shorter" gears cause the engine to turn at higher RPMs for a given road speed. The primary benefit is increased torque multiplication, providing significantly better pulling power, improved acceleration, and enhanced performance in situations like heavy towing, navigating steep grades, or off-road conditions. The trade-off is reduced fuel economy due to the engine working harder and spinning faster. These ratios are preferred for vocational applications, heavy hauling, and operations where maximizing pulling power is more critical than minor gains in fuel efficiency.

Finding the right balance between towing capability and fuel efficiency depends entirely on your specific operational needs and typical cargo weight.

Common issues

Heavy-duty truck axles and driveline components are built for durability, but like all mechanical systems, they can experience wear and issues over time. For the International LT, common issues related to the axle and driveline typically include:

• Ring & Pinion Whine: A persistent howling or whining noise that changes with road speed and load, often indicating wear or improper setup of the ring and pinion gears. This can be exacerbated by contamination of the differential fluid, improper backlash, or excessive wear.

• Carrier Bearing Wear: The bearings that support the differential carrier can wear out, leading to growling noises, especially when accelerating or decelerating. This wear can also cause play in the drivetrain.

• Limited-Slip Clutch Wear (if equipped): Trucks equipped with limited-slip differentials may experience wear in the clutch packs, leading to chattering or clunking noises during turns, or a reduction in the limited-slip action. Over time, contaminated fluid and heavy use can accelerate this wear.

Regular maintenance, including differential fluid changes at recommended intervals, is crucial for extending the life of these components and catching potential issues before they become severe.

Find a driveline shop on Repairius.