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According to Cass aka Doctor Diff, the TruTrac's have an design issue that doesn't stabilize the splined components that the axles fit into allowing them to move around inside the TruTrac carrier. He says it's the only differential that he has seen designed with no provision to set that clearance inside the unit. He spoke with them about it, and hears similar vibration and early wheel bearing wear stories all the time from all over the world.