Whistling noise in rear of my ‘06 4Runner

I’m not a mechanic, but here’s what I know.

  1. The noise does not happen until I’ve reached about 50+ mph. Once it starts it continues at low speeds.

  2. The noise will increase to a higher pitch when I start to brake, BUT it fades away after I fully brake.

Because it get higher pitched as I brake, it leads me to believe it’s a brake problem. However I recently (2 weeks ago) had all new pads and rotors put on.

Has anyone else encountered this and know what I should do to fix it?

It seems the thing to do is return to the place that did your brake work and see if they can solve this.

Thanks @VOLVO_V70 but I’m trying to isolate the possible causes so that I can let my mechanic know ahead of time so that he’s not wasting his time. He’s usually very busy. I’m wondering if there is something loose? Any help would be appreciated!

Guesses could be dust guards or possibly seating of brakes, but I think the best option is to do what volvo v70 said if it is some simple oversight they can find it in a jiff. You paid for service, they can make it right or find what it is, for probably free.

If you didn’t have this whistle before the brake job, I would take it back and have them check their work.

If it was there before the brake job, it could be wind whistling through a small rust hole.
I’ve also found whistling from a damaged roof rack that the wind can enter.

Yosemite

Could be a body whistle. Especially if this didn’t start coincident w/the brake work. Make sure all the windows are fully rolled up. Roll each down a little, then back up so it is fully seated. If that doesn’t solve it, then look for anything on the body panel that’s even a little bit loose or missing, like a piece of trim, door seal or molding, etc. Look underneath the car too, esp the plastic air dam at the front edge, and the plastic liner for the wheel wells.

A couple things: 1) They may have put on metallic pads which can do this. I think they came with ceramic pads from the factory and 2) If they put rear rotors on, maybe the parking brake wasn’t adjusted perfect. Try using the parking brake a few times to see if that helps adjust up the parking brake shoes.

One other thought:
Does the noise increase to a higher pitch when you let off the gas and coast at higher speeds (50+ mph) but don’t touch the brakes? I drive a newer 4Runner and had a Tacoma previously that both had a bit of rear differential noise when slowing down (unloading the pinion gear) and when braking slightly but also faded when braking fully. Just something else to consider.

Thanks for your help guys. Got some bad news today. Turns out the right rear axle is bent. I’m looking at dropping $450 with a Toyota dealership. I can’t seem to find just the right rear axle shaft anywhere online for my ‘06 4Runner.
I was supposed to leave for vacation in 4 days. Now idk what to do.

Chances of getting this fixed in 4 days are slim so rental vehicle is in the picture. Next call a local salvage yard and tell them what you need . If they don’t have one they can use the national locating service . Any good mechanic can solve this, you don’t need a dealer for a 12 year old vehicle.