need help with whining noise

Gear whine would be my guess. Does it have aftermarket gears?
It could also be bearings but I have never heard of bearing problems with the 8.8's and gears are more probable.

usually. Does it have aftermarket gears? If you don't know tell me what RPMs you turn in 5th gear (or overdrive) at 70 MPH. To completely rebuild the rear end it would break down something like this:
All from memory but should be close
new gears: $200
new bearings: $150
new trak-lok clutches: $60 for stock replacement $115 for carbon fiber cobra setup
new fluid: $25
XL3 friction modifier: $16
Labor took me 10 hours and I had a grease pit and a press and bearing pullers and separators and air tools. A shop will charge 7 hours labor I am guessing. I'm not sure what labor runs in your area but around here it's $80/hr.