Whistle noise on acceleration, 3.0 Diesel

s219 · May 29, 2020

I test drove a 2020 Sierra SLT with the 3.0 diesel, and loved the engine. Would have bought the truck but it made an annoying whistle noise on hard acceleration. Almost like the noise a windshield leak would make, but directly tied to my right foot on the accelerator. I tried revving the engine while in park and the noise did not happen, so it seems like it's tied to either load on the engine, airflow over the vehicle, or maybe motion of the drivetrain. HVAC on/off made no difference.

Anybody run into this before? I did a search and have seen a few older threads about whistle noises, but they didn't seem to correlate to a 2020 diesel (production in early March).

It's sort of funny, I was enjoying the faint turbo whistle (very familiar with that sound) thinking how quiet and refined the engine is while cruising, then this other whistle blared out at me whenever I dipped into the throttle. I could even control it by getting on/off the throttle. Fascinating to think about, but no way I would buy the truck like that.

The salesman said he'd have a dealer tech look at it, but I am not optimistic they really care enough to dig into it.

19Sierra · May 29, 2020

I don't have the 3.0l diesel my 19 sierra with 5.3l had a whistle that would occur during the same scenario that you described. I wired the flapper in front of the muffler open for the heck of it and the whistle has completely disappeared while not noticing a change in anything else. I had a thread in the engine and exhaust section but it didn't get much response. I will attach that thread in case you wanted to take a look.

Edited May 29, 2020 by 19Sierra

BurnsMax · May 30, 2020

It could have been the truck was in a DPF regen when you were driving it. I get more of a whistle while the truck is going through the cycle.

s219 · May 30, 2020

About how often does this engine do a regen? The truck had about 100 miles on it from test drives.

steve841 · May 30, 2020

I have the 3.0 . although I've never floored it ... wouldnt that sound be the turbo whine?

Edited May 30, 2020 by steve841

s219 · May 30, 2020

1 hour ago, steve841 said:

I have the 3.0 . although I've never floored it ... wouldnt that sound be the turbo whine?

Definitely not a normal turbo noise. The whistling on acceleration was an additional louder, lower frequency, and fluctuating noise on top of the normal turbo whistle. I thought the turbo whistle was very subdued and refined, and just perfect. This other noise sounded wrong and out of character with everything else.

BurnsMax · May 30, 2020

11 hours ago, s219 said:

About how often does this engine do a regen? The truck had about 100 miles on it from test drives.

It is usually once per tank of fuel. It varies on when it does it. It will do more often if it has been idling a lot or small short trips. Then it will do a regen every 100-200 miles

s219 · May 30, 2020

Well, the dealer had it idling for 15 minutes before I drove it, and I know that is not good for the DPF. And it had been taken on a long test drive overnight by another customer, and no telling what they did (the HVAC settings were all out of whack and I can just picture somebody's cold wife sitting in the passenger seat complaining). So it's very possible it was due for a regen at just 100 miles. That could have been it. I probably only drove it for 15 minutes altogether, and it may have been in regen the whole time.

Would there be an indicator on the dash when an auto regen happens?

I am extremely familiar with regens on Tier-IV tractors, and it can be a pain in the butt. I end up avoiding idle and keeping RPMs up during operation, and that helps avoid manual regens or inconvenient regens. I hope the truck is less finicky.

BurnsMax · May 30, 2020

A regen lasts 10-20 minutes depending on the driving conditions. There is no way to know it is in a regen unless you are using a OBD2 reader and app. The only time there would be something on the display is when there has been several unsuccessful regens. Then there is a message that comes up stating to keep driving.

My guess it was in a regen. When you put the vehicle in park it will shut down the regen process. So that whistle will go away

Edited May 30, 2020 by BurnsMax
added info

s219 · May 30, 2020

If it shuts down in park that would also explain why the sound went away when I stopped in a church parking lot to listen. So it's sounding more and more like maybe this was a regen.

BurnsMax · May 30, 2020

12 minutes ago, s219 said:

If it shuts down in park that would also explain why the sound went away when I stopped in a church parking lot to listen. So it's sounding more and more like maybe this was a regen.

Yes I can confirm it shuts down in park. I have an OBD2 reader and it shuts down when placed in park and then when it's placed in drive it will go back into the regen if it wasn't finished after a minute or two of driving.

2016 Sierra Owner · May 30, 2020

So you park that truck back at the dealer. Thank the salesmen for his time and keep looking.

yousaveone · June 2, 2020

I've got 10K on my 3.0 and can't hear or notice anything from the engine while driving.

Try test driving another. I LOVE my truck LTZ 4wd that gets 30MPG YES PLEASE!

jboyle0128 · August 7, 2021

On 5/30/2020 at 7:52 AM, BurnsMax said:

It is usually once per tank of fuel. It varies on when it does it. It will do more often if it has been idling a lot or small short trips. Then it will do a regen every 100-200 miles

I have 15k miles on my '21 LM2 Duramax Crewcab Z71. I installed the CTS3 monitor so I can watch exhaust temps, boost, EGTs, and a million other parameters. The exhaust note does change when it goes into a regen. It gets lower and almost throaty. If I am towing heavy (7k plus)then it will do a regen every 240ish miles. The CTS3 tells me exactly how many miles since last regen. No towing and a mix of city/hwy driving it goes about 620 miles between regens. The truck is phenomenal on fuel. I average an easy 23mpg (hand calc) with no towing, but I don't baby it and run with traffic. Hand calculated always shows better than the dash mpg number, usually by half to one mpg. We took a trip from KC to Omaha and averaged 28.4mpg with the cruise set at 79. When I tow my 8.5x20 enclosed I usually get 11 to 12mpg. And that's with a Jeep, generator, fuel jugs, tools, probably 8k lbs behind the truck. Again not hypermiling or anything. The cameras make towing a breeze. Never again will I tow a camper or enclosed trailer without the transparent trailer camera setup. Saves my marriage every trip.

Bob-2021 High Country · July 21, 2022

I have a 2021-Silverado High Country with 3.0 Duramax with 42k miles. I am having the same issue described above. This is the second time this has happened. The first time, about 6 months ago the whistling sound finally went away after a full new tank of fuel. Not sure what is causing the whistling noise during acceleration.