21 AT4- Metallic clinking/ rattling noise when slowing down….

[Brandon_210TX]

Curious if you’ve had any new developments or worsening of symptoms?
I have a 2021 AT4 that has a vibration or grinding sound very noticeable especially when slowing down or under 18 MPH.
Local dealer inspected & claims all normal?

I’m coming up to 5,000k soon and still noticeable rattling/clinking around 13-18 mph on Decel and now even noticing the sound right before i come to a stop. I’m thinking of taking it in this weekend to the dealer, getting oil change and having them EXAMINE everything and possibly have them drive it around so they can hear it.

 

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[chaos]

If possible, get it on video, in their own parking lot if needed. That way when they say that it's all okay, you have video evidence that it's not.

 

[Kevpak24]

Just recently I’ve started to here a slight metallic rattle/clinking when slowing down. Doesn’t happen when accelerating but happens when slowing down just before coming to a complete stop. Anyone else having this issue?

As anyone with this issue had there tranny fluid drained?? I had this same issue almost since new (4k miles on Currently). Finally took it to my dealer couple weeks ago. They drained the tranny fluid and found filings. Long story short - they replaced the planetary differential which had a knick in a gear tooth. Were close to putting in a new transmission but assured me this was the problem. No more jake brake. Problem fixed! Think I'll have them drain tranny fluid again before warranty is up just to make sure its staying clean.

This was my post in the "22' Transmission Issue <1k MIles"
Similar story - Coming from a 13' F150 Ecoboost. Have had my AT4 since December. Almost since new it has had a bad rattle at low speeds. If your going 5-20 mph and let off the gas it sounds like a baseball card in your bicycle spokes or even a jake brake. Just got it back from my dealer earlier this week. They drained the tranny fluid and found filings. Ended up replacing the planetary differential - had a gear tooth chewed up. All good now. 3500 miles - Haven't towed anything with it yet. Just glad they could get parts to fix it.

 

[Gabed23AT4]

As anyone with this issue had there tranny fluid drained?? I had this same issue almost since new (4k miles on Currently). Finally took it to my dealer couple weeks ago. They drained the tranny fluid and found filings. Long story short - they replaced the planetary differential which had a knick in a gear tooth. Were close to putting in a new transmission but assured me this was the problem. No more jake brake. Problem fixed! Think I'll have them drain tranny fluid again before warranty is up just to make sure its staying clean.

This was my post in the "22' Transmission Issue <1k MIles"
Similar story - Coming from a 13' F150 Ecoboost. Have had my AT4 since December. Almost since new it has had a bad rattle at low speeds. If your going 5-20 mph and let off the gas it sounds like a baseball card in your bicycle spokes or even a jake brake. Just got it back from my dealer earlier this week. They drained the tranny fluid and found filings. Ended up replacing the planetary differential - had a gear tooth chewed up. All good now. 3500 miles - Haven't towed anything with it yet. Just glad they could get parts to fix it.

I really appreciate the feedback fellas!
Adding to my post…
Took the AT4 into local dealership for the same vibration - this time they changed the tires (all 4) & the sound is GONE!?
Claim now is the factory installed tires were sitting too long & they have flat spots???
Anyone heard of this?
Anyhow, awaiting GMC approval to cover 4 new tires

 

[chaos]

I really appreciate the feedback fellas!
Adding to my post…
Took the AT4 into local dealership for the same vibration - this time they changed the tires (all 4) & the sound is GONE!?
Claim now is the factory installed tires were sitting too long & they have flat spots???
Anyone heard of this?
Anyhow, awaiting GMC approval to cover 4 new tires

I mean...maybe? I know mine was sitting for a couple months in Mexico, based on the build date and when I actually got the truck. I'm assuming they were waiting on components. Although my experience with flat spotted tires differs from what I experienced with the drive-line noise and vibration while coasting on level ground from about 20mph.
With the issue I have, it's very sudden, and giving it gas or braking will stop it. Tire flat spot vibrations are entirely speed dependant. I am mostly sure it has something to do with the DFM tuning at low speed and load. I am not able to recreate in L9, but I'm unsure if that's due to the DFM being disabled or the difference in transmission shift points.

 

[Brandon_210TX]

Got my “7500” (only have 6400 odometer) change today and added the noise to the list to check. They came back with the “oil was low 2 quarts and now that we’ve added, they could not replicate it”. Low and behold not even a mile after driving it and Deceling between said speeds as before, there it is again. Wondering if I should even bother going back again soon. I can replicate it but sometimes the AT tires drown out much of the rattling out but to me it’s noticeable……I also have tried the L shifting and it doesn’t happen when I down shift between gears. Only when it’s in D does it happen

 

[Pauly1]

I really appreciate the feedback fellas!
Adding to my post…
Took the AT4 into local dealership for the same vibration - this time they changed the tires (all 4) & the sound is GONE!?
Claim now is the factory installed tires were sitting too long & they have flat spots???
Anyone heard of this?
Anyhow, awaiting GMC approval to cover 4 new tires

I’m coming up to 5,000k soon and still noticeable rattling/clinking around 13-18 mph on Decel and now even noticing the sound right before i come to a stop. I’m thinking of taking it in this weekend to the dealer, getting oil change and having them EXAMINE everything and possibly have them drive it around so they can hear it.

I have a 2021 AT4 with the 6.2 L GAS engine. It makes a metallic rattle noise at cold start that mostly goes away after about a minute. It also makes the metallic rattle when deceling coming to a stop. Had it into the dealer right after I bought it and they said it was normal and sounded like air?
I had a Ford that I traded in on the AT4 that did the exact same thing and the Ford dealer said it was normal as well. After a couple years and 40k-50k miles later Ford had to replace the timing chain , guides and tensioner. After doing some research on GMC, it seems like they have had issues with timing chain tensioners! It is my opinion is is a timing chain rattle.......but as usual dealerships have no mechanics anymore to diagnose only service techs that look for codes.

 

[Pauly1]

New to this forum. I have the same rattle issue at cold start and at deceleration coming to a stop. Had the same issue with the Ford I traded in on the 2021 AT4 WITH 6.2L gas engine. Ford claimed it was normal also until a couple years old and about 40k50k miles it got so bad they had to replace timing chain, guides and tensioner. I believe it is a timing chain rattle but good luck getting a dealership to diagnose the issue. After some research looks like GMC has had an issue with the timing chain tensioner in the not so distant past!

 

[ShapeShifter]

Add me to the list of people with this problem. Get the rattle at cold start for a couple minutes and every time I roll to a stop around 14-15 mph. Got it on video (see link below). Doesn’t happen in L9. Truck has 2,500 miles.

Dealer today told me it was a belt and tensioner. They replaced the belt and tensioner. Problem did not go away. Bringing it back on Friday for further diagnosis.

Anyone ever get a definitive diagnosis on this? Is this just the way these things sound? If so it doesn’t bother me. I just don’t want to be driving around causing further damage to my truck if it’s not a normal sound.