I had a similar whining noise most noticeable at low speeds only. At first the dealer wouldn't acknowledge the noise and then stated that it was normal noise. I was able to hear the noise the most on my particular issue, by just keeping the truck in park, opening the hood, and revving to about 2500 RPM and keeping it steady there. You could clearly hear the whining noise. Took back to the dealer and they did replace a few parts that helped remove the whining noise.
VERIFIED THE CUSTOMERS CONCERN OF CUSTOMER
STATES ENGINE HAS A WHINE NOISE COMfNG FROM
ENGINE. HEAR IT BEST AT 2OOO RPMS. PERFORMED A
VISUAL INSPECTION NOTHING ABNORMAIJ. PERFORMED A
IDLER PULLEY EXAMINATION AND DIAGNOSTIC TESTED
THE COMPONENT. PERFORMED AN ENGINE & DRIVE BELT
INSPECTION TO FIND TENSIONER PULLEYS MAKING
SOUND. FOUND THE LEFT SIDE IDLER PULLEY IS NOISY.
FOUND THE RIGHT SIDE IDLER PULLEY IS NOISY.
Installed 52Bl-956AA : TENSIONER: BELT
Installed 68518735AA :TENSIONER: TENSIONER