2019 Silverado cabin rumbles when slowing down

hotrodz37 · January 21, 2020

1 minute ago, Thejet07 said:

I clamped mine and no difference

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Yeah, remembered you did, just wasn't sure if anyone else had tried it. Doubt it makes a difference at all like you said.

STX30MAC · January 21, 2020

I called my local dealer this morning to see if they have had any other reports of this happening and if they have found a fix. Waiting for the call back.

I have a lift and I am wondering if a speedometer calibration (Hypertech in line) would have an effect on it since my tires are over sized from the stock version. I feel like it did it before the lift but that was 8k miles ago and I cant remember. I will keep posting updates on here as I get more information. Hopefully it will draw some attention from others that have the same issue to post their fix or how the dealer fixed it.

hotrodz37 · January 21, 2020

34 minutes ago, STX30MAC said:

I called my local dealer this morning to see if they have had any other reports of this happening and if they have found a fix. Waiting for the call back.

I have a lift and I am wondering if a speedometer calibration (Hypertech in line) would have an effect on it since my tires are over sized from the stock version. I feel like it did it before the lift but that was 8k miles ago and I cant remember. I will keep posting updates on here as I get more information. Hopefully it will draw some attention from others that have the same issue to post their fix or how the dealer fixed it.

I'll keep you guys posted too. My service advisor is a straight shooter and he said they haven't had anyone come in for that particular issue but said its definitely not right and they will work on getting it fixed.

Streetz · January 22, 2020

Hey guys, I have a 19 5.3 8speed and I too have the rumble, since day one. My theory is that the converter remains locked while the truck is downshifting and engine breaking. If you accelerate with light throttle and get to a cruising speed at around 30mph, you can feel it locked. I am familiar with the feeling because iv experimented a lot with locking a converter manually at different scenarios like on low speeds (different vehicle). Its the only thing that makes sense. I think this was mentioned in this thread.

If this is the case then it could likely be solved via software to disengage the lockup when engine braking at low speed.

hotrodz37 · January 22, 2020

Hey guys, I have a 19 5.3 8speed and I too have the rumble, since day one. My theory is that the converter remains locked while the truck is downshifting and engine breaking. If you accelerate with light throttle and get to a cruising speed at around 30mph, you can feel it locked. I am familiar with the feeling because iv experimented a lot with locking a converter manually at different scenarios like on low speeds (different vehicle). Its the only thing that makes sense. I think this was mentioned in this thread.

If this is the case then it could likely be solved via software to disengage the lockup when engine braking at low speed.

I agree with you on this one. The 2020 loaner I have doesn’t do it nearly as bad, barely detectable. Wondering if there is TCM update the dealer can install that’s put in the newest trucks.

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Streetz · January 22, 2020

8 minutes ago, hotrodz37 said:

I agree with you on this one. The 2020 loaner I have doesn’t do it nearly as bad, barely detectable. Wondering if there is TCM update the dealer can install that’s put in the newest trucks.

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I found this information, it could be related, for now I will ride it out and see how it goes.
https://topclassactions.com/lawsuit-settlements/consumer-products/auto-news/904626-gm-class-action-alleges-transmission-shake-defect/

hotrodz37 · January 22, 2020

Just got a call from the dealer "we can't feel it, can you come ride with the tech"? Well, you should have asked that when i dropped it off since its 1:15 min round trip for me and its a workday. Unless it stopped doing it, it is VERY noticeable - so frustrating.

hotrodz37 · January 22, 2020

Alright, so went to the dealer during lunch. Rode with the transmission tech, super nice guy - he said he definitely feels it but he doesn't think its the transmission. Might be the exhaust, DFM etc but they are going to keep it and continue to diagnose. I'm not convinced DFM is deactivated in L7, so it could be that. It HAS to be the engine or trans since in neutral it doesn't do it at all. So we'll see what they come up with. Will keep everyone posted.

Edited January 22, 2020 by hotrodz37

STX30MAC · January 24, 2020

Had my 11yr old ride in the back today and asked him if he could feel it. He says “absolutely, that’s annoying Now I feel it every time but I found what’s rattling. So he stopped the rattle. I experimented in L1 today. Got up to 2500rpm then let it slow itself down. Once it gets below 5mph it feels like it down shifts and let’s loose. But of course that can’t be right it’s in 1st gear. Weird thing was that after driving In Only first gear for a while then going back to normal drive it seemed to rumble a lot less. Maybe getting the rpms up in first and second gear will open up whatever’s sticking on the down shift. I have not heard back from my service tech yet if they have had any others in the shop for this. I will call tomorrow.

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hotrodz37 · January 24, 2020

Had my 11yr old ride in the back today and asked him if he could feel it. He says “absolutely, that’s annoying Now I feel it every time but I found what’s rattling. So he stopped the rattle. I experimented in L1 today. Got up to 2500rpm then let it slow itself down. Once it gets below 5mph it feels like it down shifts and let’s loose. But of course that can’t be right it’s in 1st gear. Weird thing was that after driving In Only first gear for a while then going back to normal drive it seemed to rumble a lot less. Maybe getting the rpms up in first and second gear will open up whatever’s sticking on the down shift. I have not heard back from my service tech yet if they have had any others in the shop for this. I will call tomorrow.

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Very interesting experiment. Wondering if it’s not the transmission at all. That’s what my tech thinks. He’s pretty sure it’s engine tuning, exhaust, something of that nature. That being said, wondering if it’s something to do with the start stop system interfering with a bypass or something whether it’s on or off. Or it could be that the manual gear selection in fact doesn’t actually disable DFM like we thought.

Mine is still at the dealer, they haven’t figured it out yet but at least they’re trying!

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hotrodz37 · January 28, 2020

Dealer has been great, shop foreman took over the repair of my truck, spent a lot of time on the phone with GM documenting what was going on. GM comes back today and with a verdict of "operating as designed". Well that is unacceptable because it is not. Waiting to see what the dealer recommends from here. Might be driving a Ram sooner than I thought.

hotrodz37 · January 30, 2020

Welp, update to end the saga. They drove some trucks on the lot and a few were better than mine and a few were worse. So the dealers hands are tied by GM, so guess I’m just going to have to live with the rumble from now on. Hoping it gets better with time or that it’s a DFM issue and it will be fixed by the RANGE device once it comes out.

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lapoolboy · February 4, 2020

Switch into 4Hi and you'll find the rumbling is much less noticeable, if not gone altogether (at least on my truck).

Makes me wonder if this is not front driveshaft or CV related. I had it pre-TrailBoss lift and I have it after TrailBoss lift, so it's an anomaly in the truck itself.

hotrodz37 · February 4, 2020

3 minutes ago, lapoolboy said:

Switch into 4Hi and you'll find the rumbling is much less noticeable, if not gone altogether (at least on my truck).

Makes me wonder if this is not front driveshaft or CV related. I had it pre-TrailBoss lift and I have it after TrailBoss lift, so it's an anomaly in the truck itself.

Interesting, my truck is 2wd though so can't experiment with this unfortunately haha