FORD ID TAGS | GM RPO CODES | DANA SPICER BOM NUMBERS | VISUAL IDENTIFICATION
When repairing or upgrading differential parts, the first and most important step is to identify your existing axle / differential. Ensure accuracy by checking the tag numbers or stamps on the axle or by utilizing the RPO codes on GM vehicles.
FORD AXLE IDENTIFICATION TAGS
The location of Ford identification tags will vary by model, but most are located on a carrier cover bolt. The Ring Gear Size (differential type) and the Gear Ratio will be printed on the tag (as well as whether or not the differential is limited slip).
GM RPO CODES
GM Vehicles come with RPO codes, which are 3-character codes that designate various features / options on your vehicle. RPO codes can be found by referencing the Service Parts Identification sticker (typically located in the glove box compartment or near the spare tire), or by scanning a QR code on 2018 and up GM vehicles (located at the bottom of the driver side door pillar).
These codes contain a wealth of information about your specific vehicle's equipment and specifications. The prefix is usually F, G or H when referring to Axle Identification (for example, G80 means you have limited slip / positraction).
Note: Using the GM RPO codes to identify your axle / differential assumes that the axle / differential has not previously been modified.
DANA SPICER BOM NUMBERS
All Spicer Carrier-Type axles are identified with a manufacturing date (1) and Bill of Material (BOM) number (2) stamped on the right or left hand tube on driving axles. The BOM number may also be found on the carrier in some models as shown in illustration (2A). The axle / differential model number will often be cast into one of the webs (3). Each axle contains a gear ratio tag (4), and if the axle is equipped with a limited slip differential, it will have a tag specifying the type of limited slip lubricant to use (5).
The BOM stamp (2) or Axle Identification Tags (2A) are used to identify Dana axles / differentials. The BOM will identify the model number, the gear ratio, the type of axle / differential, and component parts.
- Traditional BOMs are 6 digits followed by 1 or 2 digits, and start with the numbers 60 or 61. On some tags, the first 2 digits won't appear on the tag, but they must be used to identify the axle. For example, you might see 3994-1 for the BOM, but the 60 has been dropped and the actual BOM is 603994-1.
- Later BOMs can start with the first 3 digits 200, but these are not typically dropped from the tag.
The BOM may be used with the Dana Aftermarket website to identify all aspects of a particular axle:
- Go to the Dana Aftermarket Media Library (http://media.spicerparts.com/media) and enter your BOM number under "Keyword Search"
- Click on the resulting literature link
- Search for the BOM within the PDF (e.g. for BOM 603994-1, the differential is a standard Dana 60 with a 3.73 Gear Ratio)
VISUAL AXLE / DIFFERENTIAL IDENTIFICATION
In the absence of an ID tag, axle / differential types can be identified using the shape of the cover, the number of cover bolts, the number of ring gear bolts, and the ring gear diameter. Use the images and information listed below to help identify which differential your vehicle has before ordering parts.
CB = Cover Bolt
RGB = Ring Gear Bolt
Spline = Axle Spline Count
