2019 8 Speed Transmission Rumble/Vibration On Deceleration

hotrodz37 · November 27, 2019

Alright guys, this is a little bit of a rant thread / a few questions. Had a 2014 that had the highway vibration, aside from that, the truck was great. Decided to get a new truck this week and was between RAM and GMC as I’ve owned 3 GM trucks in the last 10 or so years (against my better judgement after the last one). Test drive went great, was looking for everything I have read on here and didn’t notice hardly anything uncharacteristic.

Anyway, pulled the trigger on a new Denali yesterday. Have about 120 miles on it running errands around for thanksgiving today and noticed when slowing to a stop or to make a turn etc, from about 25 mph down you can feel the whole truck rumbling. Assuming it’s the torque converter locking up from second to first gear.

My question is, what is this referred to? Is it the infamous transmission shudder? Or could it be the dfm? Secondly, after the truck breaks in a little will it get better? My truck was built after the date of the new transmission fluid so it should have the new stuff in it.

Any help/advice is greatly appreciated. I want to like this truck but we’re not off to a great start here.

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Edited December 2, 2019 by hotrodz37

wizard4878 · November 27, 2019

do you have the 8 speed or 10? There is several threads on here about problems that some are having with the 8 speed, not so much with the 10. I have the 8, and once and a while I get the vibration, maybe 3 or 4 times in 14,000 miles, it only lasts a few seconds. What I have read on here is that a factory rep said most of the issue is that the trans needs to learn your driving habits. Having said that mine seems to get a little better everyday, but it was never really bad to start with, at least not in my opinion...

hotrodz37 · November 27, 2019

Thanks for the reply wizard. I have the 8 speed (in the title). I can’t see how the torque converter vibration in deceleration would get better over time though, whereas I do think it will learn and shifting will get better. I don’t have a lot of complaints with how it shifts though just the rumbling on decel. I am thinking it could be DFM related too. I’ll try and drive the truck in manual and see what happens.

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hotrodz37 · December 2, 2019

Bump,

Anyone else? Transmission is shifting pretty smooth but still have the decel rumbling from 25 down until it drops into first gear.

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B R A D · December 2, 2019

My 16 had the "infamous shudder" - if your vibrations match the RPMs jumping that's it, you'll also feel it in the steering wheel. FWIW, I don't think that's your issue.

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hotrodz37 · December 2, 2019

My 16 had the "infamous shudder" - if your vibrations match the RPMs jumping that's it, you'll also feel it in the steering wheel. FWIW, I don't think that's your issue.

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Thanks, and agreed, don’t think that’s my issue. Im going to pop it in neural when braking and see if it goes away.

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Thejet07 · December 3, 2019

Bump,

Anyone else? Transmission is shifting pretty smooth but still have the decel rumbling from 25 down until it drops into first gear.

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I’m having the same issues. Dealership refuses to change my fluids. Also, at certain consistent speeds it tumbled as well. One of many issues I have with the truck. Good luck

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hotrodz37 · December 3, 2019

I’m having the same issues. Dealership refuses to change my fluids. Also, at certain consistent speeds it tumbled as well. One of many issues I have with the truck. Good luck

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Thanks man, it’s frustrating to say the least. Really don’t know why I gave GM my money again after I had a 2013 that was bought back, a 2014 that had the highway vibration and now this one. The grass isn’t always greener I suppose, plenty of issues with the Rams and F150’s as well.

I did put it in neutral coasting from 30 to 0 and no rumble at all. So it tells me it’s the tranny or torque converter itself. I’m going to let it break in some more and see if it goes away. Only 180 miles on the truck and I’m sure tolerances are super tight.

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Thejet07 · December 3, 2019

I came from a 2018 f150 that was bought back. All manufacturers produce garbage. Which ones the best garbage is the question? I honestly like the chevy, just not mine. I have a lawyer now for this one due to multiple issues and time in for repairs. I have close to 12k on mine. I did not have the rumble initially. What I had was hard shift. After that smoothed out is when I started noticing the issue we have here. After repeated repairs that continue to persist and new issues arising I decided to throw in the towel on this one. Hopefully, my next Chevy/gmc will be better.

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hotrodz37 · December 30, 2019

Bump, anybody else having this issue and have a fix or any insight? I now have 400 miles on the truck and it seems to be getting a little better. Would resetting the TCM possibly help? My truck has the new trans fluid and shifts great other than this issue on deceleration.

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SquireSCA · December 30, 2019

Mine does it on decel, I feel vibration, and some crackling and popping from the exhaust, which I guess would normally be masked by the muffler, which I no longer have...

Figured it was that the engine braking wasn't smooth or constant due to the DFM or something...

hotrodz37 · December 30, 2019

Mine does it on decel, I feel vibration, and some crackling and popping from the exhaust, which I guess would normally be masked by the muffler, which I no longer have...

Figured it was that the engine braking wasn't smooth or constant due to the DFM or something...

Yeah, mine is only on decel from about 28-23 or so mph when it is shifting from second gear to first gear. I’m thinking it’s DFM too, but not sure. Rumbles the whole truck while the torque converter is locking up until it gets into first gear.

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SquireSCA · December 30, 2019

If/when Range puts out a box for these new motors, that will tell us what it is... If it fixes the issue, we know it is in the motor related to DFM... If we don't see it fixed, then we know it is in the Trans/Tq converter side of the equation...

I would think that if DFM is messing with the valves on certain cylinders on decel, would that not change the effective compression of some of the cylinders, which would have a direct link to how much engine breaking is taking place?

SquireSCA · December 30, 2019

Can we test that theory by putting it into manual shift mode? Doesn't that disable DFM? If it still does it then we would know it is not DFM related...

hotrodz37 · December 30, 2019

If/when Range puts out a box for these new motors, that will tell us what it is... If it fixes the issue, we know it is in the motor related to DFM... If we don't see it fixed, then we know it is in the Trans/Tq converter side of the equation...

I would think that if DFM is messing with the valves on certain cylinders on decel, would that not change the effective compression of some of the cylinders, which would have a direct link to how much engine breaking is taking place?

Totally agree here, I am going to try sport mode and M6 (assuming the new trucks deactivate DFM when in manual mode, but not sure). Looking forward to range releasing the product.

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