Gents, I have an 06 f350 cycle, under acceleration at any speed I have a hum coming from below. As soon as I let off the skinny pedal it goes away and quiets down. But as soon as any load is applied at any speed she vibrates and hums. I have checked all of the ujoints from TC back to the pinion seal and all seems visually ok. Carrier bearing doesn't have play other than the rubber starting to wear out. I have auto lock hubs..... Nothing turning up front....... Not sure where to go from here.