1. Check the Documentation:
* Owner's Manual: The most reliable method. Your owner's manual should specify the rear axle type (e.g., "8.8-inch Traction-Lok").
* Build Sheet (if available): If you have the original window sticker or a build sheet from the dealer, it will list the options, including the type of rear axle.
* Vehicle Identification Number (VIN) Decoder: Some online VIN decoders can provide detailed information about your truck's specifications, including the rear axle type. However, this isn't always completely accurate.
2. Perform a Test (Less Reliable):
This test provides a *suggestion*, not definitive proof. A true limited-slip differential will behave differently than an open differential:
* Jack up one rear wheel: Securely jack up one rear wheel. Make sure the truck is safely supported on jack stands.
* Spin the wheel: Rotate the wheel by hand.
* Observe the other wheel: If the other rear wheel rotates in the *same* direction, you *likely* have a limited-slip differential (Traction-Lok). If the other wheel *does not* rotate, you likely have an open differential.
Important Caveats for the Test:
* Parking Brake: Make absolutely sure the parking brake is *off*.
* Transmission: The transmission should be in neutral.
* Tire Condition: Uneven tire pressure or significantly different tire wear could affect the test results.
* Not foolproof: This test isn't 100% accurate. Some wear and tear on a limited-slip differential can diminish its ability to transfer torque to the other wheel.
The documentation method is far more reliable. If you can't find documentation, the test offers a reasonable guess, but keep in mind its limitations.
