How we hear noises can be very subjective (like most of things in life) so just as another data points, here is my story (case): first off all, I have not “heard” the wining noise in my 4Runner until I have read this thread (LOL)….
After reading it- it is confirmed: the wining noise is there and mostly pronounced between 2K and 4K RMP –noise is not impacted by engine load , ambient and \or engine temperature and not impacted by what gear transmission is in (Drive, Reverse, Neutral, etc..); in my case, changing to deferent type of oil had no impact on the noise (went from Mobil 1 to Shell Rotella - both 0W-20 -Full Synthetic oil with OEM filter), noise is internal, as the same noise is there with serpentine belt removed.
After above results, I have stopped by Toyota dealer and told them I want to listen the 4Runner 4.0 L V6 engine sound, result: 2019 TRD Pro (4 miles on the clock) and 2017 SR5 with 22K miles sounded exactly like my 2013 Trail (with 65K)- they both had the same “wining noise” – so at this point, I am going to call it: “characteristic” sound of this engine…
Would I wish this wining noise would not be there…? Sure, I would!
But, I also wish I would not read that thread to begin with… LOL.
My $.02
Above is what I have posted in this thread 5 years and 52 thousands miles ago (in 2019)… as of now, in 2024 my 4Runner sounds and feels exactly as it was back in 2019... :banana: