Read the chart. Compare 4WD to 4WD and there is 440# difference between the 5.3L and 6.2L models. It also translates into a reduction in the payload and trailering number for the 6.2L. This should not be new to anyone, it's been like this forever.
Look at this document here and scroll to the bottom: https://media.gmc.com/content/media/us/en/gmc/vehicles/sierra-denali/2020/_jcr_content/iconrow/textfile/file.res/2020 GMC Sierra Denali 1500 Product Guide.pdf There is 440# difference between 5.3L and 6.2L Denalis and that extra curb weight directly subtracts from payload. I don't think it is all related to the engine weight but somewhere along the line the 6.2L Denali is carrying an extra 440#.
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.
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.
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.
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.
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