Deceleration knock - 2020 Sierra Duramax

iflypigs · January 20, 2021

My 2020 Sierra Denali 3500 has had a rhythmic knock or loud tick when decelerating since new. It now has about 7K miles. It seems to be louder as the truck gets hot, especially when towing my RV. I'm not good at determining the direction of a sound, so I don't know if it is engine or trans. I've read the thread on this forum about the knock at idle, but this sound is not heard when stopped at idle, only when taking foot off the accelerator pedal to decelerate or going downhill....not braking.

I took the truck in at about 500 miles to get interior warranty work done and told them about the noise. They just said "could not duplicate". When I took it in to a different dealer for the first oil change at about 6k, I told them about it. They did not even try to duplicate the noise. The service rep said that GM says the noise I described is coming from the DEF pump and is normal. My friend has the same truck (except 2500) with about the same miles. His has never heard this noise.

Anyone aware of this noise and/or another forum thread discussing it?

CAMPINGCPL · January 20, 2021

I have a 2020 Silverado 2500. It's done it ever since I've had the rig

paticus · January 22, 2021

Same here on my 2020 Duramax Denali. I presume it's normal.

rmsmis · January 26, 2021

It is perfectly normal for these engines. It is most noticeable when you are towing a trailer or going down a hill since these will cause more engine braking due to the weight pushing back through the drive train. I do also suggest that you utilize the engine brake switch in either of these cases as it will flare the turbo to create backpressure there as well for additional deceleration.