How to Read an Axle Identification Tag

by Kevin Owen
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Automobile manufacturers place vehicle specification information in a series of numeric and alphanumeric codes on the rear axle near the rear differential. These codes usually indicate the date the axle was manufactured, the plant in which the axle was manufactured, a Bill of Materials (BOM) code that can be looked up to identify a replacement part, and the gear ratios for the rear differential. This information is important when replacing the rear axle on your vehicle as it is essential to replace the rear differential with a compatible gearing setup.

Step 1

Identify the ratio tag on the axle. It is normally located on the side of the rear differential that is closer to the front of the vehicle. This ratio tag will state required gear ratios for the rear differential for your specific vehicle and usually ranges from 2.50:1 up through 4.30:1.

Step 2

Decode the manufacturing date. The date code is usually represented with a single digit number, a single letter, and a two digit number such as 8D22. The first number refers to the last digit of the most recent year prior to the model year of the vehicle. Therefore, for a 2009 model year, the axle was manufactured in 2008. The letter refers to the month: "A" represents January; "B" represents February; all the way through "L" for December. Therefore, the "D" in this example represents April. The last two digits refer to the day of manufacture. An axle with a date tag of "8D22" for a 2009 model year car was manufactured on April 22, 2008.

Step 3

Read the Bill of Materials code that appears next to the date code on the long tube side of the rear axle and write it down. This code is generally six digits with a hyphen separating the last digit from the first five, such as 12345-6.

Step 4

Find this Bill of Materials Code in an axle BOM catalog or in the Internet database found on the vendor's website to find a comprehensive list of replacement parts, assembly diagrams, gear ratios, and vehicle manufacturer's information.

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