How Do I Identify the Limited Slip Rear Axles of a Ford 150?

by Robert Bayly
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Rear axles come in two flavors, "open" and "limited-slip." The open rear axle only provides power to one rear wheel. Limited-slip axles transfer power to both wheels, yet allow the wheels to turn at different speeds when turning corners. Determining what type of limited-slip rear axle a Ford F-150 has can be accomplished two ways. After 1968, Ford cars and trucks have an axle code on a "Certification Plate," located on the driver's door. Ford rear axles also have an identification tag located on the rear axle itself. This information is used when purchasing replacement parts, a replacement rear axle, changing gear ratio or just talking shop with your friends.

Step 1

Locate the vehicle certification plate located on the inside edge of the driver's door near the door latch.

Step 2

Locate the information at the area on the tag marked "axle," or "ax." Write it down. You will need to look it up on the chart provided in the References section.

Step 3

Locate the axle identification tag on the rear axle on the differential cover bolt in the 12 o'clock position. The number in the lower left-hand corner is the gear ratio, for example, "3.08." If the number has an "L" in it, for example, "3L08," it is a limited-slip axle.

Step 4

Locate the number immediately to the right of the axle ratio. It identifies the ring gear diameter, for example, "8.8." Write it down. This is how the rear axle is described: "8.8" would mean you have an "8.8" rear axle.

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