Engine knock a 500 miles

chiropractor · December 16, 2019

Yup, that is the knocking sound! I was going to take mine back to the dealer tomorrow believing that it was a rod bearing spun!!! Only have 200 miles on my LTZ 3500. It is sad to say but I'm happy that your truck is making this noise too. Truly, a rod knock has a more metallic clunk to it, this sounds much like an air compressor piston pumping if you were to eliminate the electric motor and belt sounds!! It almost has to be some sort of pumping sound for oil, antifreeze, transmission cooling or something like that. Yes, the 2020 engine is the same as 19 however the changes include enhanced cooling and the new Allison 10 speed. Maybe GM could explain!

redwngr · December 19, 2019

On 10/28/2019 at 11:09 PM, bass mechanic said:

heres a video with the sounds

That video has all the normal dmax ticks and rattles AND it has a KNOCK that isn't normal to my ear.

I've listened to lots of videos' that owners think are a problem, but that I consider 'normal'.

The KNOCK/THUD in the video isn't anything I'd consider as normal.

Someone that is not used to hearing all the noises that a dmax makes probably doesn't recognize the KNOCK as being unusual - so can't/don't pick it out from the other noises.

Edited December 19, 2019 by redwngr

Turtlern56 · December 19, 2019

Today I seen another 2020 Denali in an empty parking lot and I parked about 3 spots away. Turned my truck off cracked the windows and it was running. We could hear same knock on that truck but wasn’t terrible loud but even my kids could distinguish the sound. I agree on the air thumping sounds (Compressor like) Especially sitting in the truck with the door open or window cracked. My truck now has 1000 miles on it. In the mornings with a cold remote start it will do the same knock for a split second Just Enough for 2-3 knocks then quiets down for a minute or two then comes on strong. Once the truck has been running for 5-10 mins it knocks obnoxiously loud. Driving us crazy! 500-1300 rpms or so it’s very audible. Knock knock knock knock I hear it in my sleep. Lol

Roadrunner45 · December 19, 2019

Just took deliver of my 2020 yesterday afternoon. Right when I started the truck I keyed in on this same thudding sound. It seemed to be present at idle and through the first 3 or 4 gears. My previous Duramax was an LMM and I am used to the ticking sounds but this didn't sound right. I mentioned it to my salesman and asked him if we could start another 2020 which we did and no thumping noise. Brought it to the service managers attention and had him listen to it he picked up on it as well but wanted his diesel tech who had already left for the day to hear it. Taking it back to service tomorrow will provide an update later. But here's a lesson learned from a previous Chevy purchase. 2002 1500 5.3 Liter. Obnoxious ticking noise from time of purchase let the dealership influence my opinion took delivery of the truck was hoping it would go away driving it some new motor and all. Never did subside took it to a dealership closer to home and the diagnosis was it was common to the engine group. Having some time to listen to other 5.3's absent the noise took it back to the dealership I purchased it from shop foreman came out listened to it said it was the same as previous service department it's common to that engine group. Stood my ground and made them take a detailed look into the condition. Low and behold they found a collapsed lifter, repaired it no more ticking sounded like the other quite 5.3's and I was finally a happy camper.

Sonny James · December 21, 2019

I'm test driving 2020 3500HD Denali's now. I have a 2017 2500HD Denali currently which for sure does not make this noise. I've test driven (5) 3500s and (1) 2500. Two of the 3500s and the 1 2500 have made this noise, so 3 out of 6. They all have less than 30 miles on them. The 3 trucks that made the noise did so after I pulled into a parking lot and threw them into park. They continued making the noise at low idle during the remainder of the drive. I don't remember the 3 others making the noise but I also drove them without pulling over and putting them into park.

Not sure of the correlation here but Bass Mechanic has nailed the noise in his video. I am going to drive a couple 3500s again that I drove before the 3500 that makes the noise and put them through a rigorous set of tests to see if I can get them to make the noise as well. I will report back. Should be this Monday.

Edited December 22, 2019 by Sonny James
Went back to my notes and learned I had more information

Sonny James · December 21, 2019

Also have noticed when driving around 35-40 mph at around 2K rpm there is a distinct whining noise.

Edited December 22, 2019 by Sonny James
Went back to my notes

dwoods123 · December 23, 2019

Our new 2020 Sierra 2500 HD Duramax has this too. Knocking is driving my better half crazy! Never owned a diesel before but we noticed this did not seem right. Asked the tech, sales manager and others and all say it is normal after it warms up on the 2020's. Hard to believe it but I guess I'm glad others here are seeing the same thing... Will be interesting to see if a fix comes out for it or if it is what it is!

dwoods123 · December 23, 2019

On 12/19/2019 at 4:41 PM, Roadrunner45 said:

Just took deliver of my 2020 yesterday afternoon. Right when I started the truck I keyed in on this same thudding sound. It seemed to be present at idle and through the first 3 or 4 gears. My previous Duramax was an LMM and I am used to the ticking sounds but this didn't sound right. I mentioned it to my salesman and asked him if we could start another 2020 which we did and no thumping noise. Brought it to the service managers attention and had him listen to it he picked up on it as well but wanted his diesel tech who had already left for the day to hear it. Taking it back to service tomorrow will provide an update later. But here's a lesson learned from a previous Chevy purchase. 2002 1500 5.3 Liter. Obnoxious ticking noise from time of purchase let the dealership influence my opinion took delivery of the truck was hoping it would go away driving it some new motor and all. Never did subside took it to a dealership closer to home and the diagnosis was it was common to the engine group. Having some time to listen to other 5.3's absent the noise took it back to the dealership I purchased it from shop foreman came out listened to it said it was the same as previous service department it's common to that engine group. Stood my ground and made them take a detailed look into the condition. Low and behold they found a collapsed lifter, repaired it no more ticking sounded like the other quite 5.3's and I was finally a happy camper.

Let us know if you find out anything on this. Would be good to know as it is so prevalent in these from the looks of it.

DLS1 · December 27, 2019

Just bought a new 2020 Duramax. 500 miles and hear the knock. Louder when warmed up. It is at dealership now for diagnosis.

dwoods123 · December 27, 2019

17 hours ago, DLS1 said:

Just bought a new 2020 Duramax. 500 miles and hear the knock. Louder when warmed up. It is at dealership now for diagnosis.

Keep us informed on the diagnosis or if it is "normal" lol!

Joeypaul13 · January 9, 2020

Took Delivery of my 2020 LTZ a couple weeks ago, The day i purchased it I heard the THUMP sound before i even drove it off the lot. I brought it to the attention of the tech and also the manager. They both heard it and did seem to show somewhat of a concern, but it was left at that. I asked to go start another 2020 they had on the lot and the thump was there very faintly but not as loud as mine. But from what I've concluded the noise doesn't get loud and annoying until the engine is warmed up. If i had let that other 2020 they had on the lot warm up for 5-10 minutes I"m willing to bet the same sound would have developed. Really hoping GM comes out with a fix for this, its super irritating, very noticeable inside and out of the cab. We all need to complain enough so they will take action!

dwoods123 · January 10, 2020

Ours is going in Tuesday for this as well as the missing rubber strip on the roof! I will see what they say it truly is....

hogcard · January 12, 2020

my 2020 GMC 2500 does the same thing. Didn't notice it brand new. Have about 400 miles on it and starting to notice. Brake pedal also has a weird vibration to it like the anti lock brakes are trying to engage or something. Probably will take in and have both looked at.

Sonny James · January 13, 2020

I test drove a lot of 2500HD and 3500HDs since 12/2019. Some had the same level of noise as in Redwingr's video. I just bought one that has a much quieter version of his (at temperature - 180 degrees) with 50 miles (mostly put on by me). I am hoping it won't get louder by 500 miles like everyone is reporting. I warned the dealer I will be coming back if it does. I am taking a video when I pick it up in case I need to show the dealer before and after noise if necessary. Will give everyone an update at 500 miles.

Muleytime · January 14, 2020

My AT4 is making this exact "thumping" noise as well. I notice it more after driving and the truck warming up. So, those who are comparing to new trucks on the lot, I think you may need to drive them a few miles and then do the checking. I bet all of them thump eventually.......normal or not, I would like to know what it is.

Edited January 14, 2020 by Muleytime