I have a 2008 Denali with a whine in the drivetrain. It is not bad but I know I have a bearing somewhere going south. I have yet to determine where it is coming from. I have put it on Jack stands and ran it in gear while crawling under with a stethoscope trying to find the guilty bearing. So far I still don't know if it is Front or Rear, have not ruled out the transfer case. Unfortunately the Denali has full time 4x4 so lifting it on jack stands causes some drivetrain chatter and does not really allow spinning the axles at 50 mph to find the noise. I may end up pulling the driveshafts one at a time to see which eliminates the noise. Sometimes a sound will travel under your car and mask where it originates. Can be a pain to find. At this point I suspect it is a rear diff carrier or pinion bearing failing but still not willing to tear it down till I can really isolate the problem. I am open to any tricks that help show where the noise is.
I know I could leave it for another 30,000 miles while hoping it gets louder and I can find it but I like things to work properly and quietly. Already replaced all fluids, no change in noises.