2021 Tahoe - Vibration/Shuttering at 40 MPH & Light Acceleration

[cschrinel]

Hi all - I would appreciate ANY insight! I have a 2021 Chevy Tahoe with 45K that vibrates/shutters at 40 MPH and under light acceleration around 25 MPH. It is most noticeable when I put the cruise control on at 40 MPH. It does not do it when going up or down large hills but mainly on flat stretches with very small inclines going up and down. It feels like I am going over rumble strips when the steering wheel is vibrating. It has been to the dealership 5 times and the following is what I have gotten from the dealership:

The initial visits before bumper to bumper warranty was up, we were told it was operating normally. The last visit before the warranty was up they mentioned they felt the vibration but it was the tires. We knew what we were feeling there was NO way this could be accurate. However, we had the tires replaced. I specifically mentioned I felt it was something with the engine or powertrain and was told if that was the case it would be covered to 60K miles.

The tire change had zero result on the vibration so we took it to the dealership again. I informed them I did some research and there is a technical bulletin out for the SAME EXACT symptoms we have been having which states it could be a torque converter. They keep it for a week and said they were feeling the vibration but wanted us to come drive it so we could let them know if it was the same thing. During the drive, the technician captured some data and stated he could not see any torque converter issues in the data. When it does shutter the techician says if they put it in manual mode immediately it does not do it, so it is something with active fuel management because when manual mode is activated it puts the system back into V8 mode and disengages active fuel management. Does this sound correct/plausible? My limited knowledge would lead me to believe it does not shutter in manual mode because it is not trying to shift between different gears. I am not sure I understand how shuttering is related to active fuel management.

After the last visit, they now think it is a valve on the muffler which is $1000 and not covered under any warranty. The limited research I have done shows the valve is only for noise suppression and has nothing to do with active fuel management. Being that the technical bulletin symptoms is exactly what I am experiencing, I am wondering if maybe the torque converter could be the issue but just not to the degree where it would show up on any data the technician is trying to capture.

Any help/insight on this is appreciated!!

 

[GMCnewbee]

There are folks on this Forum who know a lot more than I do and I am sure they will be responding to you. My advice is to try other Dealers if you can. Some of them can be very helpful and do have Techs that know what they are doing.

 

[BacDoc]

In my opinion as a driver with limited to no experience in working on cars and trucks, I think I can say with certainty that the symptoms are definitely not muffler related!
The service department definitely doesn’t inspire confidence!

Besides transmission, maybe there’s something wrong with the “driver alert” system? Every thing you describe ( vibration with rattle) is similar to what I get when I get close to the edge of the road or turning lanes without deploying the turn signal, if that makes sense. Maybe try canceling the alert features like lane correction or parking alerts?

Any way just putting this out there

 

[2024 White Tahoe]

Hi all - I would appreciate ANY insight! I have a 2021 Chevy Tahoe with 45K that vibrates/shutters at 40 MPH and under light acceleration around 25 MPH. It is most noticeable when I put the cruise control on at 40 MPH. It does not do it when going up or down large hills but mainly on flat stretches with very small inclines going up and down. It feels like I am going over rumble strips when the steering wheel is vibrating. It has been to the dealership 5 times and the following is what I have gotten from the dealership:

The initial visits before bumper to bumper warranty was up, we were told it was operating normally. The last visit before the warranty was up they mentioned they felt the vibration but it was the tires. We knew what we were feeling there was NO way this could be accurate. However, we had the tires replaced. I specifically mentioned I felt it was something with the engine or powertrain and was told if that was the case it would be covered to 60K miles.

The tire change had zero result on the vibration so we took it to the dealership again. I informed them I did some research and there is a technical bulletin out for the SAME EXACT symptoms we have been having which states it could be a torque converter. They keep it for a week and said they were feeling the vibration but wanted us to come drive it so we could let them know if it was the same thing. During the drive, the technician captured some data and stated he could not see any torque converter issues in the data. When it does shutter the techician says if they put it in manual mode immediately it does not do it, so it is something with active fuel management because when manual mode is activated it puts the system back into V8 mode and disengages active fuel management. Does this sound correct/plausible? My limited knowledge would lead me to believe it does not shutter in manual mode because it is not trying to shift between different gears. I am not sure I understand how shuttering is related to active fuel management.

After the last visit, they now think it is a valve on the muffler which is $1000 and not covered under any warranty. The limited research I have done shows the valve is only for noise suppression and has nothing to do with active fuel management. Being that the technical bulletin symptoms is exactly what I am experiencing, I am wondering if maybe the torque converter could be the issue but just not to the degree where it would show up on any data the technician is trying to capture.

Any help/insight on this is appreciated!!

I know it is a completely different vehicle, but when the transmission failed on my former vehicle, a 2015 Expedition Limited 4x4 (purchased new - no towing), it was preceded by the “rumble strip” feeling when lightly accelerating on level pavement, or a slight uphill incline at about 30 - 45 mph.

 

[BacDoc]

Another idea

For $150 (maybe) you can get the Carbyte and just plug it in. It de activates the DFM (and auto stop) if it eliminates the symptoms then you have your answer!

If it doesn’t eliminate symptoms then you have more data to go on and it’s probably a good investment if you plan on keeping it. Kind of like a win win situation. Keep us posted.

Good luck bro!

 

[blanchard7684]

The tire change had zero result on the vibration so we took it to the dealership again. I informed them I did some research and there is a technical bulletin out for the SAME EXACT symptoms we have been having which states it could be a torque converter. They keep it for a week and said they were feeling the vibration but wanted us to come drive it so we could let them know if it was the same thing. During the drive, the technician captured some data and stated he could not see any torque converter issues in the data. When it does shutter the techician says if they put it in manual mode immediately it does not do it, so it is something with active fuel management because when manual mode is activated it puts the system back into V8 mode and disengages active fuel management. Does this sound correct/plausible? My limited knowledge would lead me to believe it does not shutter in manual mode because it is not trying to shift between different gears. I am not sure I understand how shuttering is related to active fuel management.

After the last visit, they now think it is a valve on the muffler which is $1000 and not covered under any warranty. The limited research I have done shows the valve is only for noise suppression and has nothing to do with active fuel management. Being that the technical bulletin symptoms is exactly what I am experiencing, I am wondering if maybe the torque converter could be the issue but just not to the degree where it would show up on any data the technician is trying to capture.

Any help/insight on this is appreciated!!

GM put in two things to control the symptoms you are seeing (ironically):

On the torque converter they put counterweights and a special damper on the turbine section of the torque converter to dampen the torsional vibration response from running in DFM. They also added a hokey exhaust flapper to change the acoustic response in the exhaust.

Here is a thread that shows this valve. This valve has been known to make other noises and the thread shows what others did to defeat this valve very easily.

Exhaust Butterfly Valve Chirp

Can someone instruct me where this Exhaust Butterfly valve is located and how to "pin it open". I think mine is chirping. Thank you. 2016 Yukon XL Denali

www.tahoeyukonforum.com

Yes it is plausible (although a bit of a stretch) that the "flapper valve" in the exhaust is causing the issue. If it is stuck in the wrong position it may change the exhaust response. This might be a part of the problem.

From that thread you can see how you can use about $5.00 and a trip to home depot to rule this out of the source of issues.



However it could also be the torque converter.

The condition you describe is a classic if not text book torque converter clutch wear issue. The symptom occurs because there is material built up on the stator from the friction disc on the turbine section. This is similar to material transfer on your brake rotors causing a shudder.

If the use history at 45K miles is a ton of towing or stop and go driving it may be a material transfer issue. The transmission cooling I've seen has been very aggressive and so material transfer hasn't been a widespread issue.

Putting transmission in L9 will disable DFM operation. If the vibration goes away in L9 the torque converter clutch operation may actually change by strategy, meaning that the torque converter clutch engagement may change with DFM enabled or disabled. I'm not 100% certain on this but I'd be surprised if the strategy for torque converter clutch is same.

The other variable engaged and disengaged with DFM is the counterweight and damper functions in the torque converter. This could be a reason why the symptom goes away with DFM disengagement.

(note that running in L9 or using a DFM disabler is a strong recommendation if you want the engine and transmission to last as long as possible. )

Using a scan tool can check for the proper input and output response but it isn't going to check for vibration. Put another way, the scan tool will only show if the torque converter (as well as rest of transmission) is being controlled properly. The I/O response will be just fine on a mechanically damaged torque converter clutch.

Here is a very useful video that shows the gory details of the 10 spd torque converter.

At 7:50 he shows the torsional counterweights and spring dampers.

The first 8 minutes overall is a good description of the 10 spd torque converter and you can see what the stator surface looks like as well as the friction material on the turbine section.

If locking open the exhaust flapper doesn't change anything then I'd suggest the following are the main issues

Transmission fluid is spent--maybe time for a full change of transmission fluid.
Torque converter clutch is damaged from excessive material transfer
Counterweights are getting stuck in position from wear...may describe why it goes away in L9
Rivets holding the damper section in place are loose or worn... may describe why it goes away in L9.
Valves in the valvebody may be causing some misoperation of the TCC. this is unlikely though if the tech's scan tool showed all the I/O was working normally.

So outside of a full fluid exchange...yes it can still be a torque converter with an outside chance that the valvebody is suspect.

 

[cschrinel]

f locking open the exhaust flapper doesn't change anything then I'd suggest the following are the main issue

GM put in two things to control the symptoms you are seeing (ironically):

On the torque converter they put counterweights and a special damper on the turbine section of the torque converter to dampen the torsional vibration response from running in DFM. They also added a hokey exhaust flapper to change the acoustic response in the exhaust.

Here is a thread that shows this valve. This valve has been known to make other noises and the thread shows what others did to defeat this valve very easily.

Exhaust Butterfly Valve Chirp

Can someone instruct me where this Exhaust Butterfly valve is located and how to "pin it open". I think mine is chirping. Thank you. 2016 Yukon XL Denali

www.tahoeyukonforum.com

Yes it is plausible (although a bit of a stretch) that the "flapper valve" in the exhaust is causing the issue. If it is stuck in the wrong position it may change the exhaust response. This might be a part of the problem.

From that thread you can see how you can use about $5.00 and a trip to home depot to rule this out of the source of issues.



However it could also be the torque converter.

The condition you describe is a classic if not text book torque converter clutch wear issue. The symptom occurs because there is material built up on the stator from the friction disc on the turbine section. This is similar to material transfer on your brake rotors causing a shudder.

If the use history at 45K miles is a ton of towing or stop and go driving it may be a material transfer issue. The transmission cooling I've seen has been very aggressive and so material transfer hasn't been a widespread issue.

Putting transmission in L9 will disable DFM operation. If the vibration goes away in L9 the torque converter clutch operation may actually change by strategy, meaning that the torque converter clutch engagement may change with DFM enabled or disabled. I'm not 100% certain on this but I'd be surprised if the strategy for torque converter clutch is same.

The other variable engaged and disengaged with DFM is the counterweight and damper functions in the torque converter. This could be a reason why the symptom goes away with DFM disengagement.

(note that running in L9 or using a DFM disabler is a strong recommendation if you want the engine and transmission to last as long as possible. )

Using a scan tool can check for the proper input and output response but it isn't going to check for vibration. Put another way, the scan tool will only show if the torque converter (as well as rest of transmission) is being controlled properly. The I/O response will be just fine on a mechanically damaged torque converter clutch.

Here is a very useful video that shows the gory details of the 10 spd torque converter.

At 7:50 he shows the torsional counterweights and spring dampers.

The first 8 minutes overall is a good description of the 10 spd torque converter and you can see what the stator surface looks like as well as the friction material on the turbine section.

If locking open the exhaust flapper doesn't change anything then I'd suggest the following are the main issues

Transmission fluid is spent--maybe time for a full change of transmission fluid.
Torque converter clutch is damaged from excessive material transfer
Counterweights are getting stuck in position from wear...may describe why it goes away in L9
Rivets holding the damper section in place are loose or worn... may describe why it goes away in L9.
Valves in the valvebody may be causing some misoperation of the TCC. this is unlikely though if the tech's scan tool showed all the I/O was working normally.

So outside of a full fluid exchange...yes it can still be a torque converter with an outside chance that the valvebody is suspect.

Thank You so much! This helps alot!

 

[cschrinel]

f locking open the exhaust flapper doesn't change anything then I'd suggest the following are the main issue

 

[cschrinel]

Thank You so much! This helps alot! As a follow-up, I did some test driving and noticed the vibration/shuttering is not present when in manual mode at all. For example, I tried L7, L8 and L9. Since DFM is disabled only in L9, would this indicate it may not be a DFM issue? As you also mentioned, this may also be due to the torque converter changing strategies or the counterweight and damper function being disengaged.

Also, if were an exhaust flapper issue wouldn't the vibration be present in manual mode. Thanks!

 

[jfoj]

A few other comments.

Not sure if the ignition timing advance behavior is the same between the 5.3l and 6.2l but at least on the 6.2l lower RPM tip in throttle the ignition timing maps are screwed up and the timing is Retarded very heavily and this gives the feel of a misfire or fish nibbling on a baited fish hook. It is very obvious if you get the right conditions and have a seat of the pants feel for it.

The other problem is with internal transmission valve body leaks causing transmission and/or torque converter slippage. The more mileage with a leaking valve body, the more likely to cause other premature transmission wear.

I would consider a transmission fluid change to see how much debris is in the transmission pan. The new fluid may help the situation as well. Even if the transmission fluid change and pan inspection does not resolve the problem, at least the fluid chance could rule out the transmission fluid contributing to the situation.

The torque converters are programmed to slip a lot on these vehicles and this can cause premature torque converter clutch wear. This might be evident in the transmission pan??

The last thing could be a bad cam lobe that is worn due to the roller lifter needle bearings failing. This would be a bit tough to troubleshoot and diagnose depending on how badly the cam wear would be. Just another fun thing to consider.