Truck Forums - Rear diff sounding like my ex wife during decel ... WHINING !!

Greetings,
For a minute there, I thought she was back when I heard all that whining coming from the rear of the truck .... Thank God it's just a mechanical meltdown and not the return of the BFH ....
Enough humor, the problem is that while cruising at or above 40 mph I hear a whining noise coming from the rear diff when I take my foot off the go pedal .... This is a 2006 Chevy 3500 Dmax/Allison .... I talked to a couple friends and they actually argued about what they thought the problem was .... First of all, I did check the oil and it was full.
One person said it was a pinion brg going and the other said my R&P were shot .... Can someone please shed a little light on this for me .... I'm not a big rear end guy ....
Thanks,
Doberdewd