Brake noise on first start of the day

This whining noise only happens the first time I start the truck for the day, and back out of my parking spot. My shop couldn’t find the cause, and it didn’t make the noise for them, because it had already been started that day.

They said the brakes are fairly new, so that wasn’t the cause. Any ideas? The Dropbox link to the video I took is here:

https://www.dropbox.com/s/u8xmq5pwkj3tao0/out_2021-01-17-01-01-25.MP4?dl=0

 

Mine does this too so it's not just your rig. Seems like after you drive a bit it stops.
But even when rolling real slow with the brakes applied it will still squeel a little.
but not as loud as when cold. I think it's the rear brake drums that resonate.

 

Normal you are getting the flash rust off the rotors

 

NVH (noise , vibration, harmonics)
usually its hard to get rid off especially if lightly applying brakes while backing up, if its in the rear you can try removing drums, cleaning out all the dust, and re-adjust brakes, that might be enough to rid you of the noise

 

Mine does the same thing, when I leave work to head home. More so after just washing my rig. I've already bought some shoes and drums to replace next weekend. Otherwise it comes and goes.

 

It's not flash rust on the rotors. I have looked at the front rotors Shining like new
and get in and go to leave and it's singing when brakes are pressed.
With windows down stereo off it sounds almost exactly like it's coming from the rear brakes.
Not the front.

 

Mine does this also.
It didn’t used to do it as loud as it does now.
But I do have 136k on the rear drums.
I haven’t cleaned them in a long time.

It only does it the first time applying the brakes.
Not always, but more often than not when backing up.

It does sound like it is the rear.
Honestly haven’t been too concerned about it to check it out.
I need to though

 

Mine screams too, but only when they are wet from the last time I parked. Surface rust. It's hard to pinpoint the sound. It sounds like the front, but I think it's the drums in back. I'd only worry if it squealed like that all the time.

 

Thanks everyone, it’s annoying, but glad it’s not a safety issue. It goes away when it warms up.

 

The shop is going to try again, but this time I’ll leave it there overnight, so it does it for them in the morning. I’ll report back what they find