nluchau

Hey bud, was your's doing the jerks or was it actually clunking? Can you refresh me on exact symptoms again? Thanks!

I know I beat this like a dead horse but I'm at now almost 31k miles and still experiencing the downshift jerks when slowing down. I feel them at 5-4, 4-3, 3-2, 2-1. It almost feels like a tie up of gears or someone tapping the brake when it occurs. I've had the taps reset a couple of times and also the valve body replaced. Nothing has fixed it. Also I feel a lunge or surge sensation on occasion when slowing. I wonder if that is the torque converter is releasing???? Word is the torque converted is locked during Decel and unlocks and locks at each downshift. Does this sound correct? Is this still normal characteristic or has anyone gotten theirs fixed under warranty? I've tried M5 mode, I've tried turning off grade braking, nothing has corrected the issue. Thanks!

Good to hear from you again njk4o5! Mine isn't downshifting where I'll spill something. Its just annoying as heck still.

I just found this online: https://atracom.blob.core.windows.net/webinars/gm/6l50_80_90_updates.pdf 6L80 Intermittent Harsh Downshift, Chuggle or Shudder During Deceleration 5.3L Tahoe, Suburban, C/K Trucks Customer complaint may be harsh forced downshifts or the chuggle/shudder during a coast down intermittently. This is considered “Normal” with this powertrain package. It is a self test for the O2 sensors. Test runs with the vehicle speed above 45 MPH (72 kph) in 6th gear with the TCC applied. The ECM drives the fuel system rich and then into deceleration fuel cutoff mode (shutting the injectors off) to check the system. Test will end during the deceleration and fuel is restored. (This typically causes the Shudder/Chuggle shift feel in the vehicle). Aggressive throttle response during this system check mode will cause the vehicle to have a “Harsh” downshift (this happens because the TCC remains applied during the test). If the test runs while in 5th gear, the TCC will not be applied and the complaint will not likely occur. Note: The test is designed to occur one time per key cycle, but can run up to 10 times if aborted due to throttle input. Mine isn't intermittent as it does it all the time, it doesn't go away in M5.

Are you guys experiencing what I am specifically? When I go above 40 and coast or easy brake to a stop. When its doing the 4-3, 3-2, 2-1 downshifts I feel a jerk or a tie up sensation and a release when it downshifts. I also see the RPM's bump up (which is what I should see). The jerks or bumps or tie up sensation feeling has been occurring since new on my 2016 5.3 6 speed. I've brought this up quite a bit here but there tends to be no fix insight. The dealer replaced valve body and TCM and has reset taps but nothing has fixed it.

I thought I'd bump this again, anyone else dealing with it? I'm at almost 30k and if its something I can have fixed under the bumper to bumper the time is now. Only thing they have done is reset taps a couple of times, replaced valve body and TCM and that is all.

Service writer called and said they pulled the belts off and everything is tight and they can't find a source of the noise. She said its quite common it makes this noise and on another like vehicle in their lot. I have yet to hear that myself. She is claiming the noise is from the fuel pressure building. I am not buying this answer at all. I told her to show me a TSB or some sort of documentation where it says this is a normal characteristic. She only brought up there is one for the extended cranking (which I know about). I am calling bull butter on this being normal. Thoughts?!?!

Truck is at dealer now for issue. I had a service writer listen to the noise I posted above.

Thanks for the reply! No I haven't. I don't even know the first thing to check. Thinking I may schedule an appt with the dealer. I'm still under the bumper to bumper. Sent from my SM-G950U using Tapatalk

When the temps get a little cooler this noise when starting is more noticable. You can hear it at the link. It's not the noise after it starts, it's during the cranking. It sounds like something squeaking. Anyone got any ideas? I have 28k miles. Link: https://drive.google.com/file/d/1GHoOHmix49UI0-qSNMnlSh2CrErCEeOw/view?usp=drivesdk Sent from my SM-G950U using Tapatalk

My understanding is they can see if the ECM was flashed and how many times. I really don't want to get into a pissing match with the dealer. I understand you guys could potentially remedy some of my issues it just isn't worth the hassle of going to court over if it came down to it. I'll continue pressing the dealer for potential remedies until my warranty expires.

Will this in any way shape or form void my warranty?

This is interesting. And maybe it has that feeling of a soft engine brake to me too but it occurs as a jerk, I can replicate the feeling when I tap the brake pedal too. Keep us posted

Thanks for this piece of info Grumpy Bear. I do find this helpful info, it really is, but heck this is 2018 we're talking about. Technology is ever so advancing and one would think that a 5.3 with a 6L80 transmission would be tried and trued by now. This isn't the first year of them. I truly feel it's all in the tune. If GM would just address this I feel they could tweak the tune to drastically reduce or eliminate these issues. Give me 1 mile less per gallon tune that makes a truck drive like a truck.

This is pretty much what I feel, the jerk feels like if you tap the brake. And yeah you cant throttle it during a downshift or else it'll cause it to hissy fit.