Ford Differential Axle Codes

Identifying Vehicles Equipped with OE Traction Differentials

Here we present information to assist you in making the determination of what rear end ratio you have in your Ford Motors differential.  In the second table you will be able with your Certification Plate code to locate and determine just what rear differential ratio your Ford vehicle left the factory with.  Ford rear end differentials are refered to by the diamater of the ring gear, i.e. 8.0 inch, 9.0 inch.  Links are provided in the first table set identifying the different rear end types, see  table.  Using these tables you will be able to locate the detailed information on replacement parts, upgrades and changing ratio parts and accessories for improving the performance of your vehicles differential.  Need to replace a ring and pinion ratio, want to improve power or mileage we can provide the parts you need.

Ford cars and trucks from 1968 on have an axle code on the Certification Plate that can be used to determine if the vehicle is factory equipped with a limited slip differential. The Certification Plate can be located on the lock face of the left door edge. The plate layouts vary depending on the year, but in every case the axle code section is clearly marked as either "axle" or "ax". Ford axles codes contain one or two character. Any code beginning with a letter (an alpha code) indicates the vehicle is equipped with a limited slip differential EXCEPT as shown below. Some trucks with axle codes that are numbers only (numeric codes) are equipped with limited slip differentials.  For positraction replacements and parts see the following link. 

A chart is also provided which presents Differential cover/cover gasket shapes, a common technique to identify differential ring gear diameter.  And a Dana/Spicer Differential Parts illustration showing how to locate the Dana bill of material number is provided. This is a critical number to ensure that you find correct parts the first time.  For example Dana used in some cases 3 to 4 different ring gear widths for say a Dana 35 ring gear, so the set up is not the same for each gear category.

The following figure presents differential cover/cover gasket shapes. Counting cover bolts and cover shapes is a common method to determine which ring gear diameter differential you have in your rear wheel drive vehicles. See following paragraph for selection of correct Dana parts

.

When ordering Dana/Spicer Differential Parts provide bill of material number. This number is stamped on your right hand side axle tube. It's a number like 603XX-X, 604XX-X or 605XX-X. With this number you can tell exactly what components the factory used in the assembly of your differential.