Whirring sound, most noticeable around 30-40 mph.

Hello, I recently bought a used 03 to replace my other 03. I don’t know the history of the vehicle. It has 221,000 miles on it roughly. No warning lights are on, runs good, drives good, bit has this whirring, humming sound that is associated with the vehicle speed, turning doesn’t seem to affect it, putting it into N while moving doesn’t affect it. I have checked transfer case, and rear differential oil level and they are ok. Greased the unjoints, made no difference. One of the cv boots is split so I’m thinking that may be it. Or maybe a wheel bearing. I have not checked front differential fluid level though but it doesn’t look like it’s been leaking. Any ideas would be appreciated. Thanks

 

I would guess wheel bearing. Possibly a rear one if turning doesn’t affect the noise.

 

I am going to drive it in the morning and verify that the noise is consistent while turning. Thanks

 

This could be what the Car Care Nut on YouTube calls the "airplane noise" b/c it sounds to him like a jet engine spooling up. I can't find the video and he wasn't even test driving a 4Runner, it was a Sienna or something but just as I heard the noise I was concerned about and thought, "Hey, that's the same noise," he mentioned it and said not to worry about it, Toyota transmissions just make that noise for some reason. Actually it just occurred to me that I made a video of it when I was asking around on forums. Starts about 6 seconds in.

 

I found it, it was the drivers side wheel bearing, replaced hub assembly. Noise is gone and glad of it. I was worried it was something $$$