nluchau

Same thing happened to my black truck and it was indeed bird crap. It ate through the clear and clay bar never did anything. Had it polished out but can still see where it was. This was on my 2016

Yes you need to disable grade braking at every turn on of the key and sadly this did nothing for my deceleration downshifting.

Duplicate post

I dont know if the dealer has ever done a clutch relearn on my 6L80, is that a thing if they reset taps they can do that? I know on the 8 speeds they reset them and relearn but I hear nothing about the 6 speeds. The TSB that talks about the 8 speeds having harsh 3-1 downshifts is exactly what I am experiencing with my 6 speed but it seems my issue falls on deaf ears. This is what I am referring to that doesnt pertain to my issue but I'm having almost the same issue. https://gm-techlink.com/?p=7170

Mine has this 2-3 hard shift (first one of the day) too. Then its fine.

My valve body and TCM was replaced already and the taps reset a couple of different times but that was all. I believe with the valve body the fluid was mostly all replaced? It's almost like its downshifting too early thus causing the rapid jump in RPM and the jerk/braking sensation because its not matching the speed.

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