4x4 Hubs on a F-250
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Sounds like you might have a vacum leak some where. Try taking the snap ring off the hub and give the hub a yank, it will come out. Check the O-ring for breakage. I would replace these and give the new ones a thin coat of petroleum jelly and see if this helps your problems. Also check the vacum lines that go into the hub for leaks, cracks, etc.