Re: Whining sound on decel?
If fluid levels are good, I would guess rear differential, front pinion bearing (though it could be many other things as well, noises like that are hard to isolate!)
As an overly general rule, a whine on coast can be a worn/out of spec front pinion bearing and a whine under load is a worn/out of spec rear pinion bearing OR pinion OR gears OR carrier bearings. No way to really tell without opening it up...
Some suggest tightening the pinion nut slightly to compensate for any abnormal wear...up to you, it's a cheap solution if it works, but if you OVER tighten your future will be one with a lot less cash!
The optimal (but costly) solution, since the nut uses a crush sleeve to ensure proper preloading on the bearings, is to disassemble the differential, replace any worn bearings, and then set everything back to factory spec.
Let us know how it goes!