Humming noise at highway speeds

I've tried searching the threads but I'm a newbie here and have had no luck.

2021 4Runner Premium

Issue:
On the highway, anywhere from about 55mph and up, when the vehicle is just barely maintaining speed, I hear a slight humming "ooooooooooooo" sound that goes away when I let off the throttle. This noise occurs on both cruise control and with the pedal. Generally only occurs on flat roads as the RPMs hit the magic number to make this noise, around 1700rpms I think.

Basically I only hear this sound when just enough throttle is being applied to maintain highway speed.

Thoughts?

 

Can you be more specific? Around what area it's coming from (top, bottom, front or back)? You have a roof rack? What type tires?

 

Check to see if you have differential fluid leaking , could be a bad seal/ gasket.

 

Pretty sure it’s a “normal” sound. My 2018 does it too. I think it’s a resonance sound. I can force it to happen in my truck via throttle control at about 60mph. Also, the sound got louder when I got new tires. But the sound isn’t from the tires.

 

https://www.4runners.com/threads/howling-noise-at-highway-speed.8761/

 

Needle bearing

 

No roof rack, happens on two different sets of tires. It is specifically happening when the accelerator is pressed just enough to maintain speed around 1700 RPM on the highway so around 65 -75mph is the only time I can hear it. If I let off accelerator it stops, if I accelerate it stops, it's only when maintaining cruising speed. Happens with pedal or cruise control.

 

My 164k mile 2013 is starting to get kind of growly at speeds over 63, I suspect it may be the needle bearing.

Either that or tires, mine are at 52K. I know certain tires get louder if they wear, not sure if that's the case with Grabber ATX.

 

Needle bearing sound goes away in 4wd (if I remember correctly). It’s different from the sound the OP is talking about.

 

He said the noise goes away when he lets off the gas pedal. So can not be those things

 

I’m 99% sure it’s the “diff howl”. Harmless harmonics, most often. But yeah, it’s kinda weird. You can make it happen intentionally with light throttle control and certain speeds (mine is around 60-63mph). Mine changed a bit when I got new tires. Seemed to get a little more pronounced.

 

Google “4runner diff howl” and read all about it.

 

Sounds like harmonics. Change your rear diff fluid and make sure to grease joints every 3k miles. I changed mine at only 10 months old and 3500 miles, from the factory it only had 2.5 quarts in it (1/2 quart low) and magnet full of metal.

 

I’m new on this chat forum, I’m not tech savvy . So learning how to reply on these things, bear with me .

We had to rebuild the rear end on our truck. It wasn’t a Toyota , but you can hear the howl as you speed up and it decreases when you let off the gas and slow to a much slower speed .

 

plus at only 2 years old these shouldnt go bad

 

Definitely the diff in the back. I have a similar thing after regearing on the Taco and the 4R. For me is fine, and if you are noticing a wear smell, like burnt popcorn which is the gear oil being over the threshold temp, then you are ok.
You might want to check that the breader at top is still functional and open and not damaged. If water when in and couldn't vent out then there is a chance there for expansion of the water when it gets hot. Good luck and let us know what you find out.

 

I had the same thing. Researched for weeks and finally took it to the dealer being under warranty and it ended up being my rear end. The replaced all the internals. Power train covered it. $4,300 job. Got it back, all gone. Mine is a 22 2wD but I bought used so no idea what they did prior. He said it did have some metal shavings in the fluid but nothing extreme. Im just glad my power train warranty covered it!

 

I’ve now driven three 2018+ 4Runners and I could make the sound happen in all three when I tried. So I’m convinced it’s harmless harmonics.

 

I did that just now, and yep... definitely a well-documented phenomenon!

 

This seems most close to what I've been experiencing. I may take in to the dealer just to see what they say?

 

Hi all I have a 2021 Toyota 4Runner (Full time AWD) also 4WD option

I have been having the exact same issue, I have taken to the dealer twice. First time he said it’s normal characteristics and second time he felt slight vibration, while talking the entire test drive on purpose so we wouldn’t hear the noise.

The noise is not extremely loud. I would describe it as a slight pulsation, like not a steady noise, and can feel the noise vibration as well in the gas pedal. (So hard to describe) goes away when I let foot off accelerator. Noise does not go away in 4WD) . I feel like it is on drivers side not the rear or maybe it is the rear vibrating to the front. It is driving me nuts.

[Gdawg] tell me u found the problem

 

Bumping an old thread, but I have had this issue too. At highway speeds its the 'ooooooooooooooo' sound as described by the OP. No idea what it could be from but it drives me crazy. As soon as I let off the throttle, it stops. I use cruise control all the time and it happens when the throttle picks up to maintain speed while in cruise as well.

 

Drive shaft?

carrier bearing?

only under throttle application means when load is applied. So something is worn and tolerance is poor.

 

Great, taking the 4R down to Myrtle in less than 2 weeks. There is no vibration that I feel. I also grease the propeller shaft a few weeks ago.

Its a 2020 and still under CPO warranty. I guess Ill have to risk the $160 diagnostic fee and see if I can get it looked at.

 

Did you end up taking it in for the howl? Learn anything?

 

I am very disappointed in dealers doing any kind of diagnostics. First I would look for an independent shop that specializes in the part you suspect. Dealers only follow the SHOP manual for diagnostics. So read a shop manual first and see if that makes sense to you. Sometimes dealers have electronic test equipment needed for completing the assessment -hence a good independent shop might have same or better electronic equipment.

 

I drove from OH to Myrtle this week, the humming only happens between 67-71 mph when I'm giving it gas, any faster/slower or when I let off the gas and it stops. I'm guessing it's just a resonance thing.

 

If it is a howl or some sort of harmonic and a very certain speed, then it could be the diff. There are plenty of tests and things to do to check the diff. Good luck.