The rear axle of four- and rear-wheel drive vehicles can be identified by a number of visual cues, manufacturing codes, and year, make and model of the vehicle. Axle identification tools such as DiffWizard.com can help to narrow the available options by year, make and model and provide key indicators that further identify the rear axle. Major axle manufacturers such as Ford and Dana Spicer provide manufacturing codes that can be easily decoded to identify the axle.
On a Dana Spicer axle, the manufacturing codes are both stamped onto the axle housing itself and attached with a metal tag to the differential cover. The first line of numbers typically refers to manufacturing production codes, and the second is an identifying number that can be linked to a specific axle, including information such as gear ratio, bearings and differential type. To identify a Dana Spicer axle, the bill of materials number can be cross referenced at Dana.com. Axles manufactured by Ford have a similar tag attached to the differential cover that provides information such as gear ratio, specific axle and differential type. Differentials.com has a graphic representation of how to interpret Ford axle identification codes.
Axles manufactured by General Motors, American Axle & Manufacturing, Toyota and Chrysler do not have easily translated manufacturing codes. Physical characteristics such as the shape of the differential, differential cover bolt count, axle spline count, and whether or not the axle is retained by a c-clip inside teh differential are all things that help identify axles by these manufacturers after year, make and model have been identified.