2014 GMC Sierra Denali 6.2 ltr Unknown noise.

Native82 · September 28, 2020

I have a unknown noise that is coming from what seems like the mid section of my truck. I have been to the dealership multiple times without having any luck figuring out what it is. I then took it to a private garage and they swore it was the transfer case. 2k later I have a new transfer case but the noise still persists. I then went back to the dealership and they said its probably going to be the cats going bad. Soo.. 1800 later I have new cats duel exhausts and unfortunately this persistent noise. I have a video but it won't let me up load it here, so here's a link. Check it out and let me know if anyone else has had this issue. Its driving me crazy.

Lsgun1 · September 28, 2020

That rattily sound? Kind of sounds like a heat shield on the exhaust that has broken a tack weld.

Native82 · September 28, 2020

In the beginning that's what I thought too but no one has been able to find any loose shrouds or heat shields. Its also particular when it make the noise, it will do it when going up an incline, it will do it if you have it hold the RPMs at about 1800 regardless of the gear its in. You can also feel it vibrate in the gas pedal when it happens.

midwestdenaliguy · September 28, 2020

I had some rocks kick up onto the heat shield, it's the perfect trap because they settle in certain areas and can't roll or pop back out. At certain RPM's I could hear them rattle, the exhaust was hitting the perfect note to get them to move around. Yours sounds much louder than what I experienced though. Have you tried tapping the heat shields with something to be absolutely certain there isn't anything that may be trapped on top of one of them? If there's no rattle when tapping I'm sorry to say I'm at a complete loss at what that noise is...would drive me nuts too.

da90 · September 29, 2020

Sounds like my 2014 Sierra Denali 6.2. Mine rattles at like 30mph. On mine it’s the two fuel lines from the charcoal canister going towards the engine. Have some one rev to the RPM and grab those lines and pull on them.

Sent from my iPhone using Tapatalk Pro

rlcole321 · October 1, 2020

It sounds like some sheet metal vibrating, try to look for loose metal guards or protectors

M1ck3y · October 2, 2020

Crazy... was it loudest when you were on the throttle?

Native82 · October 2, 2020

Its only makes the noise at around 1800 -2000 RPM. It doesn't matter what gear it's in, i could be turning a corner and it will do it or I could be doing 70 mph on the interstate and it will do it. I have spent hours pulling and pushing heat shields, looking for anything that could be loose and vibrating and haven't found anything. I will definitely looking at what da90 said in his comment where I can't remember if I checked those fuel lines or not. I appreciate any and all ideas you guys have, I am now starting at the beginning and going to go through the truck completely again. I had one shop say they think it might be something in the transmission but seeing this has been making this noise for 6 months + it makes me wonder why it wouldn't have gone out by now. Im not even going to go in that direction until there is no other possibility. Thanks everyone, keep em coming.

Lsgun1 · October 2, 2020

I wouldn't go into the transmission, I doubt it's inside. You've already thrown to much at it with no results so a real diagnosis is what is left not a "we think it's this with no guarantee". You can use a soft face hammer and tap all over the truck (some places harder then others so you don't cause damage) to see if you can replicate any rattles. Have you looked at the flapper valve on the exhaust?

Edited October 2, 2020 by Lsgun1