Description

Starting around 1965, Dana started using metal tags affixed to the differential cover by two of the cover bolts. Each tag has a Bill of Material Number (BOM) stamped on it and it is affixed to the axle before it is shipped from the factory. The photo shows a Build Tag (red arrow) attached to the differential by two of the differential cover bolts (yellow arrows) . Unfortunately, these tags are often missing on trucks that had prior differential service. Up until about 2005, the BOM number is a 6 digit number beginning with a 6 plus a dash number (ex: 610604-2). They can be used to determine not only the axle model, but also what components the axle was originally built with. We often ask for this number to insure we provide you with the exact parts you need for your truck.

Each different BOM number signifies an engineering part change which may be minor or major and may involve one or more parts. The dash number indicates the axle ratio.

Many axles will also have the BOM number stamped on the axle tube. For front axles, the number can be on the front of either the left or right axle tubes. On rear axles, the BOM number is stamped on the back of the right axle tube.

In addition to the BOM Tag, many axles will have a Ratio Tag secured by single diff cover bolt. If the axle has a Limited Slip Differential, the ratio tag will also have the letter "L" (ex: 3.73L).