Identifying vehicle axles can be performed by locating and decoding manufacturing codes, casting numbers, and differential tags, or by using characteristics of the axle to determine its manufacture. Differential identification tools such as those at DiffWizard.com help narrow what axles were used by year, make and model.
Visual keys, such as differential cover bolts, shape of the differential cover and whether or not the axles bolt into the housing, help identify the axles on a particular vehicle. Axles from Dana Spicer have a build of materials number etched into the tube of the axle housing that can be entered into a BOM identifying tool at Dana.com. Axles manufactured by Ford have a tag attached to the differential cover that identifies production information, axle size and gear ratio for that axle. General Motors and Chevrolet put manufacturing codes in the glove box or door jamb of vehicles. The "F," "G" and "H" codes pertain to the axles and can be identified at sites such as Differentials.com.