Originally Posted by 351w
actually the pinion doest have a real bearing it is known as a crush sleeve
Actually, the crush sleeve provides the preload on the pinion bearings, which is why it must be replaced whenever the pinion seal is replaced. There are tapered roller bearings on the pinion shaft. The pinion nut is tightened down against the crush sleeve (basically a piece of soft "pipe") until the proper bearing preload is obtained. It's similar to giving front wheel bearings a preload with the adjusting nut.....
I will agree that it sounds like either a carrier bearing or pinion bearing. I've also heard of numerous complaints of stress cracks forming in the carrier of the Ford rearends, which can cause a whirring noise as the spyders will be misaligned. Just pull the differential cover and look things over. You'll know it if something is on its way out. Pay special attention to the carrier and look closely for any visible cracks. If that lets go, plan on a costly repair.
If everything looks ok, refill it with the proper lube and, if it's a posi, add 4 oz of the friction modifer from Ford.