So mine started this a couple of weeks ago. The temperature at night has been dipping into to 20's and it sits for four or five days at a time, I don't drive it everyday. When I start it on a cold morning the transmission sounds pretty rough, really just figured the oil is cold and it is what it is. But even after it warms up it has the supercharger noise...kinda like a bad ground on a radio, it sounds like its coming from the transmission area and not the engine compartment. crazy that there is no dipstick. Will make an appointment and see what happens.
Well crap....if it is the Cats now what? how to fix? For the record mine has done it since day one so the mileage didn't play into mine. I would like to start mine with the belt off but I am afraid of what codes or check engine lights will come on or be stored, has anyone tried this yet?
No modifications and has done it since day one. My friends truck has the factory installed cat back and same noise. When I took it to the dealer they had other trucks on the lot that had the same noise, they opened a case but I have never heard anything back. Good luck tomorrow maybe you can gain some traction
I can also put the truck in gear with foot on the brake and blip the throttle to get it to make the noise...kind of a quick power brake. I will try and get a recording of it. i thought about taking the belt off and starting it to see if the noise was still there, my thought would be to narrow it down to idler, ac compressor or something that the belt is spinning. Hopefully i'm not sending you in the wrong direction but the noises seem to be the same to me.
I have the same noise, glad you were able to capture it recorded. I think mine is related to the chirp I have every time I start it after its been sitting overnight, take a look at Squeaky belt or pulley on 6.2 HC started by Beard bros. I think its the same thing i have been tracking down with no success. co worker bought a new 6.2 and has the exact same noises. It makes the same noise as a bad idler pulley.
Think I found it, there is some insulation between the door and engine compartment, it was twisted sideways and not really where its supposed to be. I can reach around and feel some loose fuzz. Just a heads up it was wet, had mud and pine needles at the bottom of the door....good place to keep an eye on for rust. I live in pretty heavy pine trees so they gathered there.
So my daughter has noticed a pine squirrel going to the AT4 and running off with black insulation while I was out of town. Saw him today and he will no longer be able to do it....I found some of the insulation but cannot find where he was getting it from. There was chewing marks all over the hood insulation but it doesn’t match, sounds like he made multiple runs. Figured maybe someone has torn in to there truck enough to help identify where it is possibly from? Some kind of sound deadening?
Picked mine up today, they couldn’t fix the noise....they could repeat the noise but couldn’t repair. Here are the notes. They started aTAC case and I asked how to check in on any progress, they told me it was internal with GM and they would update me when there is information. Upside....they aligned my bed and it looks better.....down side they scratched my door and it has to go back to the body shop
Dropped mine off today and could recreate the noise for the service manager, he heard it so maybe I will get some traction. i was checking out some of the trucks on the lot and man a lot of the beds are misaligned. I will update when they get back to me. The loaner I am driving makes the same noise just not as loud.....I'm dreading the call that this is normal for the 6.2
I am dropping mine off next Wednesday to take another shot at the squeak. I am also missing some paint on the tailgate when you unfold the step so hopefully they can take care of that to....and the bed alignment.
Thank you for the update, i believe this is what mine is doing also. I can put it in gear and hold the brake with light throttle and get the chirp to show up. Now that it may be pin pointed I will try and see if i can track it down to the PCV. I am curious if this is the same noise that I have on start up that takes 30 seconds or so to quite down. I will try to attach a video.....you can hear a tension-er/belt type noise until near the end and then it just disappears .....does this every time i start it after sitting for a couple hours and it doesn't matter if its hot or cold. IMG_
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