The first step to repairing or upgrading your differential is to correctly identify it. The best way to do that is to read the bottom line of the tag number or axle tube stamp.
Differential Identification by Tag Number
Differential tags can easily be used to identify Dana and Ford differentials.
Dana Spicer Tags
Look for The Bill of Material (BOM) number on the tag. It will identify the model number, gear ratio, type of differential, and all component parts. Traditional BOM’s are 6 digits followed by 1 or 2 digits and start with the numbers 60 or 61. On some tags, the first 2 digits don’t appear on the tag, but they must be used to identify the axle. For instance, you might see 5561-1 for the BOM, but the 60 has been dropped, and you’d need to use 605561-1. Later BOM’s may start with the first 3 digits of 200, but these are typically not dropped from the tag.
The Dana website has a great search tool called The Expert where you can enter your BOM and get all aspects of your particular axle.
On GM axles made by Dana, the Bill of Material is usually stamped in the right hand tube underneath the spring. These BOM’s normally start with 60, and the first 2 digits are not typically dropped as in some cases with Dana ID tags.
Ford differential tags are pretty straightforward. The only piece of information you have to decode is The Month of Manufacture. It’s usually represented with a single digit number, a single letter, and a two digit number such as 6F17. The first number refers to the last digit of the most recent year prior to the model year of the vehicle. Therefore, for a 2007 model year, the axle was manufactured in 2006. The letter refers to the month: “A” for January; “B” for February and all the way through “L” for December. So the “F” in this example represents June. The last two digits refer to the day of manufacture. An axle with a date tag of “6F17” for a 2007 model year car was manufactured on June 17, 2006.
GM RPO Codes
GM vehicles come with a RPO (Regular Production Option) code tag that contains lots of information. It’s usually located in the glove box or door jamb. Look for the area labeled “Service Parts Identification” and the prefix is usually F, G or H when referring to axle identification.
Differential Identification by Cover/Number of Bolts
If the ID tag or stamp is missing or unreadable, differentials can be identified by the number of cover bolts, the distinctive shape of the cover, the number of ring gear bolts, and ring gear diameter. They can also be identified by whether the center section is an integral or dropout design. Dropout differentials are also referred to as third members or pumpkins.
AAM 9.25″ Chrysler Front
AAM 10.5″ Chrysler
AAM 11.5″ GM/Chrysler
AMC Model 20
AMC Model 35
Chrysler 8″ IFS Front
Dana 28 IFS
Dana S110 Third Member
Ford 8″ Third Member
Ford 9″ Third Member
Ford 10.25″ & 10.5″
GM ’55 Passenger Third Member
GM ’55 Truck Third Member Dropout
GM 7.25″ IFS Clamshell
GM 7.5″ & 7.625″
GM 8.2″ B.O.P.
GM 8.25″ IFS
GM 12-Bolt Passenger
GM 12-Bolt Truck
GM 9.25″ IFS Clamshell
GM 10.5″ 14-Bolt
Toyota 7.5″ Early Third Member
Toyota 8″ Third Member
Toyota Landcruiser 8″ Third Member
Toyota Landcruiser 9.5″ Third Member
Toyota 7.5″ IFS Clamshell
Toyota Tacoma/T100 8″ Third Member
Toyota Landcruiser 8″ Reverse IFS
Toyota Tundra 8.75″ IFS