| How to Identify My Differential |
How To Identify a Spicer Axle
All Spicer Carrier Type axles are identified with a manufacturing date (1) and Bill of Material number (2) stamped on the right or left hand tube on driving axles. The Bill of Material number may also be found on the carrier in some models as shown in illustration (2A). For independent front suspension (IFS) axles, the B/M number may be located at one of three locations: 1) A vertically positioned tag near the center of the right hand side support arm, 2) stamped into the left hand side support arm (opposite end of the camber adjuster), or 3) stamped into the "nose end" of the axle carrier. The location of the information will depend on the manufacturing date of the axle.
The axle model number will be cast into one of the webs as shown (3), or it can be on the nose.
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 be used (5).
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It may sound silly, but there are many things to consider and lots of data to collect prior to picking up the phone to find rearend parts. Unlike engine or suspension parts, rearend parts are not easy to look up, and can vary a lot for any vehicle. Just because it has a specific engine size or transmission type does not mean that the vehicle uses one specific gear ratio. Vehicle manufacturers will usually offer at least two gear ratios for any given vehicle model. The gear ratio can vary with little or no correlation to its intended use or market area. I have seen many models released that offer four different ratios with little or no other variations in the vehicle. Another thing that complicates matters is there are really no good application books that a salesperson can use to look up the right parts for a vehicle by year, make, and model. And, for whatever reason, the VIN number is not helpful, as on most vehicles it does not give any information on the differential gear ratio or limited slip options.
One way to get the right parts to the end user is by process of elimination. In this scenario, the vendor sells parts that they think may be right until they find the right combination. This is often referred to as the "we got your credit card number and that's all that is important" method.
Don't count on your friends to identifiy the differential for you, as they may not be accurate. If the diff is not the model they say it is, there may be restock charges for sending back parts. The only sure-fire way to determine the right parts for a rearend is to find someone who really knows rearends and be prepared to answer a lot of questions. Some of the questions to answer BEFORE calling are:
How do you use or plan on using the vehicle?
Year, make (Chevy, Jeep, Ford, Dodge, etc.), model (1/2 ton, Cherokee, etc.)
Tire size
Old gear ratio
New ratio you think you want
Axle spline count
Number of cover bolts, or is it a drop out
Number of ring gear bolts
Bill of material number or tag numbers
Transmission type
Engine size (I hope you know this one, surprisingly a lot of people do not)
Engine rpm that you are comfortable cruising down the highway at. This will only work if you have a tach, and it may require driving in a lower gear to experience higher rpms.
Number of wheel lugs
Trailer Weight (For those of you who pull trailers or other vehicles)
Standard or reverse rotation front ring & pinion. This can be determined by whether the pinion enters above or below the axle housing centerline. Reverse rotation gears have the pinion shaft entering above the axle centerline and standard rotation gears enter the housing below the axle centerline.
Independent Front Suspension or solid straight axle in front.
Outer diameter axle bearings
It may seem ridiculous to have to answer so many questions, but in the end, it is far easier to order parts once correctly, than to order and return the wrong parts several times. If you take the time to find out the answers to a lot of questions, it will save a whole lot of frustration for everyone involved.
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