Rear axle codes are used to identify the specifics of an individual vehicle rear axle and are commonly found stamped on a small metal tag affixed to the rear axle of rear-wheel drive vehicles. The rear axle codes are usually mounted to the center section of the rear axle by being bolted to one of the attachment bolts securing the center section to the axle housing. Information encoded on the tag is the gear ratio, differential type and date of manufacture. Other codes are used to identify the manufacturing plant and the year of manufacture. The rear axle codes are very important if attempting to identify the gear ratio of an axle or to place the proper components in a vehicle restoration.
Represented as numbers and letters in a specific order, rear axle codes can be deciphered by obtaining information commonly found in vehicle repair manuals available in libraries and auto parts stores around the world. Many of the more popular vehicles have the rear axle codes listed online under various key words. It is usually best for people to contact a car club or collector club which is focused on the model of vehicle that requires identification and ask for decoding information pertaining to the identification tag in question.
It is important to decipher the rear axle codes when an axle is need of repair. This will allow parts to be purchased in advance instead of after disassembly and provide identification of the type of components used in the axle. Understanding the rear axle codes also aids in axle identification when searching for an axle in a salvage yard, where the axles may already be removed from the vehicle. When attempting to restore a popular muscle car or a particular performance package option, the rear axle codes will not only ensure that the correctly-optioned rear axle equipment package is installed in the vehicle, but most importantly, it will ensure the correct year axle is used in the restoration. This can lead to a numbers matching restoration that is much more valuable than a non-numbers matching vehicle.
When a vehicle is said to be a numbers matching vehicle, it is saying that the engine, transmission and rear axle codes are all correct as far as year and model manufactured, as well as equipped with the correctly-optioned components. With the right vehicle, a numbers matching vehicle can sell for more than twice the amount of a non-matching vehicle. Some collectible vehicles displaying the proper code and date tags with the right options can top $1 million US Dollars (USD) at auction.