What Is This Ringing?

[firefighter907]

I'd put my money on something in the exhaust system.

[truck_newbie]

11 hours ago, firefighter907 said:

I'd put my money on something in the exhaust system.

Thanks for giving it a listen. This is actually my 3rd exhaust system. Ringing was happening with the stock exhaust. It was actually one of my reasons for switching to a cat-back system with no flappers because I thought the flappers in the stock exhaust might have been causing this. No dice though. 

 

My suspicion lies with the transmission because if the ringing starts and there is a gear shift, it goes away then comes back a few seconds later.

 

It's so weird because it only happens under light throttle while cruising. Acceleration from a stop or acceleration from any speed doesn't cause it. 

[firefighter907]

Can you get under the truck and yank on the exhaust up front? Years ago I had a truck that made a noise like that and it was a exhaust hanger. Take a rubber mallet under there with you and start smacking stuff.

[truck_newbie]

2 hours ago, firefighter907 said:

Can you get under the truck and yank on the exhaust up front? Years ago I had a truck that made a noise like that and it was a exhaust hanger. Take a rubber mallet under there with you and start smacking stuff.

I will give that a try. Thanks. 

[BlancoSilverado]

Kinda sounds like a idler pulley going out?

[19 Denali ultimate]

That is interesting.  I can hear it for sure though.  and you are sure it is not the valve springs on the exhaust before and after the muffler causing it?

[FishHuntRepeat]

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.

 

[greco2003]

I hear it no idea what it is. Maybe something with the cylinder deactivation since it’s happened with light throttle? But no idea. Maybe bring it to the dealer and play them the sound file. 

[truck_newbie]

3 hours ago, BlancoSilverado said:

Kinda sounds like a idler pulley going out?

Will that be audible from the side of the truck?

[truck_newbie]

2 hours ago, 19 Denali ultimate said:

That is interesting.  I can hear it for sure though.  and you are sure it is not the valve springs on the exhaust before and after the muffler causing it?

Yep, I have an aftermarket exhaust now, no flappers or springs. I'm guessing you are referring to the flappers?

[truck_newbie]

1 hour ago, FishHuntRepeat said:

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.

 

Thanks FishHunt, I'm glad I'm not alone in this. I had the dealer look into this sometime last year but they couldn't reproduce it because they weren't quite sure what they were listening for. Now that I've captured it in a recording and the general consensus so far is that it's fairly audible, i'll play it for the dealership so they know what they are listening for. 

 

I followed the 6.2 squeaky thread for a while. No one in the thread reported a ringing so I didn't think it was related. I hear the squeak too but it doesn't bother me as much as the ringing. 

 

It's interesting that  you also bring up the idler pulley. I'm not sure where that is located in the engine. I can try to strap the mic near that vicinity to see if it captures it. I thought it was coming from underneath the truck. 

[truck_newbie]

55 minutes ago, greco2003 said:

I hear it no idea what it is. Maybe something with the cylinder deactivation since it’s happened with light throttle? But no idea. Maybe bring it to the dealer and play them the sound file. 

Thanks for giving it a listen. I plan to do just that. 

[BlancoSilverado]

42 minutes ago, truck_newbie said:

Will that be audible from the side of the truck?

It can be, i thought(not sure) there is a recall on the idler pulleys on the 6.2L? Some one else was saying that they had the idler and tensioner both go out/replaced 

[FishHuntRepeat]

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.

[truck_newbie]

31 minutes ago, BlancoSilverado said:

It can be, i thought(not sure) there is a recall on the idler pulleys on the 6.2L? Some one else was saying that they had the idler and tensioner both go out/replaced 

I haven't seen any recalls on the idler pulleys for the 6.2 but i'll bring it up to the tech when I take it in. Thanks.