Sounds like it might just be bearings. If you quiet down the rear end you will probably start to hear noises from the other parts of the truck that want your attention. Do you haul a lot with it? If so, change them out. Otherwise just turn up the radio and enjoy the truck. I would think once you had them out you could get NAPA or someone of that nature to match them up. By the way, is this the rear end with the square axel tubes?

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