What gear ratio do I have?  Do I have a positraction?  Ford Differential Axle Codes

Identifying Ford Vehicles Equipped with OE Traction Rear Ends

Ford cars and trucks from 1968 on have an axle code on the Certification Plate, information on this plate can be used to determine if you vehicle is factory equipped with a limited slip positraction rear end - differential. The certification plate can be located on the lock face of the left door edge. The plate layouts vary depending on the model 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 pickup trucks with axle codes that are numbers only (numeric codes) are equipped with limited slip differentials.  If you need positraction replacements and or parts see this link. 

One common technique to identify differential ring gear diameters is cover - cover gasket shapes, to help you we have provided a list of possibilities.  We have also included link to assist you in determining what rear end you have, as well as a large list or rear end parts.

 

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.