2021 International MV Transmission & Axle Gear Ratios

This guide provides detailed information on the transmission and axle gear ratios for the 2021 International MV, helping owners and technicians understand their truck's driveline specifications.

Transmission gear ratios

The 2021 International MV was available with a variety of transmissions, primarily automatic. The most common options were the Allison 2500 HS (Highway Series), RDS (Rugged Duty Series), and 3000 Series.

Allison 2500 HS/RDS

Allison 3000 Series (5-speed)

Allison 3000 Series (6-speed)

Available axle ratios

International offered a wide range of axle ratios for the 2021 MV, catering to different applications and performance needs.

How to identify your axle ratio

Identifying your International MV's axle ratio is crucial for proper maintenance, parts ordering, and understanding its performance characteristics. International trucks, like many commercial vehicles, typically have a build sheet or spec sticker that details all installed components, including axle ratios.

• RPO Sticker/Build Sheet: The most reliable method is to locate the RPO (Regular Production Option) sticker or build data sheet, often found within the glove box, door jamb, or under the hood. This document will list various codes, and among them, you will find the specific axle ratio code. This code will usually be a three-digit code or part of a larger component code for the rear axle assembly.
• Axle Tag: If the RPO sticker is missing or illegible, the rear axle housing itself might have a metal tag bolted to it (either on one of the differential cover bolts or on the housing tube). This tag contains information such as the axle model, ratio, and sometimes the build date. You might need to clean the area thoroughly to read the stamped numbers.
• VIN Decoder: For International trucks, using a VIN decoder tool (often available through International dealerships or certified service centers) can provide a comprehensive list of original specifications, including the axle ratio, directly from the truck's Vehicle Identification Number.

Towing vs MPG impact

The choice of axle ratio significantly impacts your truck's performance, particularly regarding towing capability and fuel economy:

• Numerically Lower Ratio (e.g., 3.07:1, 3.31:1): These "taller" gears result in lower engine RPMs at cruising speeds. This translates to better fuel economy on the highway as the engine doesn't have to work as hard. However, a lower ratio reduces the mechanical advantage, meaning less torque at the wheels, making it less suitable for heavy towing or hauling. It will also feel slower to accelerate from a stop.

• Numerically Higher Ratio (e.g., 4.56:1, 4.88:1): These "shorter" gears cause the engine to turn at higher RPMs for a given road speed. This provides a greater mechanical advantage, delivering more torque to the wheels, which is ideal for heavy towing, hauling large loads, or operating in hilly terrain. The trade-off is generally worse fuel economy, especially at highway speeds, due to the engine working harder.

• Balanced Ratios (e.g., 3.55:1, 3.73:1): These ratios offer a compromise between fuel efficiency and towing capability, making them suitable for mixed-use applications where the truck might tow occasionally but also spend time on the highway unladen.

When specifying an International MV, it's crucial to match the axle ratio to the primary intended application to optimize either fuel efficiency or towing performance.

Find a driveline shop on Repairius.