So I'm chasing a seemingly unbeatable whine sound from my motor, I've replaced everything that runs off the serpentine belt, plus the water pump, and the sound was still there.
After running the motor without the belt I don't hear the sound anymore... thing is I've already replaced most everything people have suggested. Tensioner, AC Compressor, Alternator, Idler Pulley, Power Steering Pump/Pulley, Water Pump, Serp Belt...
I'm lost 🙃🙃

 

I have this also, whine goes up and down with rpm drop as the transm shifts. No whine in idle but give some gas and you start to hear it,. I thought it was transmission but maybe not?

I unplugged the alternator to see if the whine stopped - with no effect. The index line for the tensioner is on the edge of the indentation rectangle and the belt looks to be in good shape and moving smoothly, though when idling I can see the pulley moving a little. Fluids are topped off.
Any advice" Car runs and shifts fine.. for now.

 

well i am having the same issue as you, and have narrowed it down to the harmonic balancer , they have a slim piece of rubber sandwiched between the pulley and balancer that comes loose and slips , get under the front and see if the balance has any wobble to it as well , .

 

I'm having a similar issue and can't pin it down either.
I've noticed that mine only occurs when the truck is in gear, and doesn't happen if I rev it while it's in park or neutral. My best guess is that it's something to do with the transmission or torque converter.