Mine has been making slight whining noise since day 1. I'm not too concerned. It's a Toyota. They all make weird noises.
It's probably coming from the transmission. I changed transmission fluid to Amsoil Full Synthetic Fuel Saving ATF, when I installed a heavy duty transmission cooler. The noise was completely gone after that but after a thousand miles I could hear it again although not as noticeable.

OP, have you checked your transmission fluid level and condition? The fluid in my 4Runner was well worn out at 20k easy miles. It was darkish brown in color. I have not done any towing or off-roading with it. I will do drain and refill again in a few thousand miles, with Amsoil ATF. Fluid is cheap, transmissions are expensive.

My 4th gen made a whining noise. Drove me nuts for about 200,000 miles. I THINK it was the power steering pump.

My 5th gen makes a small whining noise too. I gave up caring about it. Maybe in 200k more miles....

I have the similar 2012 T4R SR5 V6 4.0L started doing it right after I booted the truck one morning, engine was not fully warmed up yet. (my guess is the oil pressure rushed higher when engine was cold, collapsed or clogged part of the oil filter when engine was booted and now was restricting the oil flow to the pump). It probably is your oil filter or the oil cooler.

The noise itself I am pretty sure it comes from the Oil Pump starving of oil ( because of cavitation), but the cause is "restriction" before the oil pump (oil filter failure or oil cooler/or line clogged). First swap the oil filter with a Wix or Toyota factory one and see if the "whine goes away" try one or more filter choices as well if one does not deliver results.

If that does not solve it, look at the oil cooler itself or a clogged oil line, replace that with a factory one. I am due for an oil change and will see if my whine noise is solved. Right now I am at 106k km's. Here is the same type of noise and problem from Nissan 4x4 blog: https://www.thenewx.org/forum/11-pow...e.html

Could also be: whining noise coming from the secondary timing chain
system. Nissan V6 4.0L engines had the same issue, Nissan launched a bulletin to fix the issue.

YouTube
https://www.clubfrontier.org/forums/...-ntb09-128.pdf

2014 limited 4x4 with 60k miles.

My wife and I purchased this 4Runner from an individual 3 months ago. We absolutely love this rig but it’s developed a crazy annoying whining noise upon acceleration. It can be in park, neutral, or driving down the road it doesn’t matter. I took it to the local Toyota dealership and they basically told me that they’ve seen this on several 4runners lately but they haven’t been able to find a solution! They’ve tried replacing pulleys, belts, and even the alternator on several different 4runners with no luck. So they logged the problem in there database and advised me to keep checking back with them for a solution. Basically keep driving it and hope that enough people complain to get Toyota’s attention for a fix! I’ll try to post a video so you can hear it. If they can’t fix this noise then I’m just going to sell it.

Just here to share my experience in hopes it will help somebody. I have a 2014 Trail edition with 60k. It started making an unusual whining noise that was very noticeable during acceleration a couple thousand miles ago. I removed the belt and briefly ran engine before taking to dealer in hopes it was an accessory or idler pulley making noise. Noise was internal. The dealer confirmed noise was not normal. The technician disconnected transmission from engine to isolate the noise and found that it was coming from the engine. After discussing with Toyota field tech that just happened to be on site that day they removed driver side valve cover and reset the timing chain tensioner on that side. Noise went away but returned after several minutes. At this point they removed the engine and replaced the timing chain, tensioner and guides under warranty. It has been about 500 miles since the repair and I’m very happy to say that the very annoying whining noise is gone.

We just purchased a 2014 T4R with 87k miles, coming from a V8 4th Gen, same exact noise and it's been driving me crazy. You can hear it revving the engine sitting still and you can definitely here it while accelerating, seems to be loudest between 2500 and 4500 RPM.

Briefly asked the shop foreman at a local Toyota dealer and he thinks it's an idler pulley. I'm going to yank the belt of and see if it still makes noise. This thread has been very informative, thanks for posting!

Call me crazy, but this seems like it's nothing. And after 9 years of this engine on the road with no chronic failures documented related to a whine in the engine, I'm not going to worry about it. This engine is a noisy bastard, and after my first two Toyotas, I've just come to expect it.

I've seen these threads play out here, the FJ forum, and Tacoma forum.
Never seen a solid 100% fix for this, nor do I remember an engine failure from it.

Some have changed the timing chain or tensioner and had the noise go away for a bit.
Others have changed the oil filter and it may quiet it.

Guess it's irritating and not much more.

Mine just started making the same noise at just under 40K miles. Irritating for sure. Will be taking it in for service due to recall, so will have them check this out and see if they find anything.

Update on mine (or lack there of): 125k now same as ever. Planning on doing about 2500-3000 miles this month with no reservations. After 75k almost of ownership with it like this it just sounds normal to me. I’m not worried unless people start having related failures.

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

YouTube

Mine has been whining like normal for 167,000 miles. I think it's just the nature of VVT.

For future people that browse this post, here is the noise:
Outside in park free-revving: YouTube
Inside during acceleration: YouTube

I got underneath with a stethoscope and it sounds like its coming from the transmission pump, you can hear it particularly well though the lower transmission cooler line. The noise is extremely annoying and drives me crazy, but for now I am using @VWHillbilly's advice and turning up the radio.

For what it's worth, I've been paying attention to other 4Runners on YouTube and in the wild and unfortunately this noise seems to be very common.