2017 5.3L/8 speed lugging at throttle tip in

SGS_Z71 · January 1, 2018

Hoping you guys can weigh in on my issue I am having with my 2017 LTZ. Has 9,900 miles on it now, with the 5.3 /8 speed, 3.42 4x4. I have been searching forums and posts a lot but can’t seem to find any solutions to my problem. When I leave my house in the morning, on a 25 mph road I can feel a chugging/lugging (feels like the same thing as when trying to drive a manual trans in too high of a gear at low speed). It happens if I put in M7 to lock out AFM, so that is not what I feel. Not a big deal, but I am feeling it now when I tip into the throttle, most noticeably on hills on the freeway. Mash the gas to get a downshift, no problems. I’ve taken to the dealer, had the trans tech ride with me. The closest thing thing the tech could do on the computer was lock/unlock the torque converter. He explained how the tcc is pulse width modulated, versus on/off, so slip is variable. After driving around, he basically said there is nothing that can be done and he can’t reproduce the issue. He felt it once, and believes it is spark knock and suggested running higher grade fuel for a tank. I am planning to get into a bigger battle with the dealer, but I really don’t want to hand them over my truck for days/weeks until I’ve done some more homework. I assure you they will feel it after driving it for a few days. I have been unable to find anything specific to the 8 speed other than torque converter shudder, which I am not having. The best I could find was “chuggle”, which seems only to apply to the 6 speed. There are no codes, check engine lights, etc.

Do you guys have any tips on how to steer this to resolution (TSB, etc). I may be wrong, but I think it is a transmission item, not engine.

Love the truck, but this is just something that I can’t get used to or deal with. My 2014 Sierra 4.3 6 speed didn’t do this.

Thank you anyone for any tips to get this resolved.

Bash74 · January 2, 2018

If there are no codes and it is hard to reproduce it will be a battle to try and get something done. Now the weird thing is I know a few people that had shifting and chug along issues but after they lifted there truck and changed to 4.11 gears all the shifting and response issues where gone. In my 15 never had any issue with shake or vibration like alot have talked about but also lifted the truck from day one. I just think the trans, torque converter, drive shaft, rear gear setup is not right on these trucks. I was going to upgrade to a new truck but after testing ford, dodge, toyota, and chevy and found issues with all of them decided to stay with my 15.

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SGS_Z71 · January 4, 2018

The trans tech pretty much told me I needed to have it tuned to correct what I am explaining 100%. I don’t want to void my warranty though. I just hope someone else has this issue and had it resolved. I’ve never had such a choppy throttle, oh and the random jerks or not moving right away when trying to back out of the garage.

I was hoping to convince them to flush the trans and wipe the adaptive learn to see what can be done. In the mean time, I’ve filled it up with 93 and will see if it makes a difference.

Obscenejesster · January 4, 2018

I don't know if it's the same issue or not but with my 6 speed, I only felt what you are talking about at full throttle. Under normal driving, I did not feel it.

After switching to 93 octane, I know longer get this feeling at full throttle.

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SGS_Z71 · January 5, 2018

I have ran 1 tank of 93 now, no difference. Temperature and fuel doesn’t change it whatsoever. It only happens when I tip into the throttle to accelerate without a downshift. It gets worse the more I “lug” the engine.

I am going to probably talk to another dealer and/or let them drive it for a week with data logging to see if they can catch what is occurring when they feel it.

Anyone have any TSB’s or experience correcting similar issues?

SGS_Z71 · January 9, 2018

My dealer gave me a big speech about a TSB and that there is no fix at this time, but I could run my truck in M5 to disable AFM. I reminded them that I had an 8 speed, and it would be M7. They responded with that they thought I had a 6 speed and would get back to me. Now, they aren’t getting back to me. I’ve since spoken to another dealer in parallel and they acknowledge that they are starting to get complaints on 8 speeds, but that there are no updates available at this time.

Either way, my truck still does the issue when I lock out AFM in M7 at low speeds. I got it on video, when in 4th gear around 25-30mph, the truck is doing about 1150-1200 rpm, it jumps about 100-150rpm when I feel it.

If I am on the highway above 70, it is turning enough rpm’s to not lug the engine when in m7. Put it back in normal and you can feel it lug when trying to accelerate under load without a downshift.

If I was 100% positive disabling AFM stopped it, I would just deal with it and tune down the road. But the fact that it still does it in M7 bothers me. It also does it in tow/haul mode, but it downshifts more frequently when towing, so you don’t feel it.

At this stage it appears my options are:

#1 deal with it and hope an update occurs

#2 tune the truck and void my warranty

#3 deal with it until 60k then tune the truck

#4 trade off for another brand

Love everything else about the truck, just frustrating.

Anyone??

SGS_Z71 · January 9, 2018

On 1/1/2018 at 8:45 PM, Bash74 said:

If there are no codes and it is hard to reproduce it will be a battle to try and get something done. Now the weird thing is I know a few people that had shifting and chug along issues but after they lifted there truck and changed to 4.11 gears all the shifting and response issues where gone. In my 15 never had any issue with shake or vibration like alot have talked about but also lifted the truck from day one. I just think the trans, torque converter, drive shaft, rear gear setup is not right on these trucks. I was going to upgrade to a new truck but after testing ford, dodge, toyota, and chevy and found issues with all of them decided to stay with my 15.

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Thinking more about your response, this would cause the truck to turn more rpms right? Maybe gets it out of the “lugging” range? Who knows

BamCam · January 9, 2018

My brother has a '17 Sierra and I have a '17 Colorado with the exact same issue. Brother's truck has had the flush done twice and a new torque converter and problem still exists. GM is involved and will be data logging truck this afternoon. His truck is actually worse and almost undriveable at this point.

The more I read posts like this and others I believe his never was trans shudder but a ECM/TCM programming issue (torque management). Our driving styles are very similar and 1/2 our commute is on the same roads, so this may explain why we both have it and not that we are just unlucky. I believe the dealer was too quick to diagnose as shudder and went down the wrong path initially. I too have believed it to be shudder but now I am not convinced my "shudder/chugging" is the infamous trans shudder that is cured with flushing.

I am growing concerned this will never be resolved without 3rd party tuning.

Bash74 · January 9, 2018

Thinking more about your response, this would cause the truck to turn more rpms right? Maybe gets it out of the “lugging” range? Who knows

I can say from my experience with my truck before I changed gears the vehicle would have that bogged down feeling almost like trying to start off in 3rd or 4th gear in a manual transmission, but once gear change the truck just felt alive when stepping on gas. Even before I lifted the truck and had a tune it still didn't have the response it does now. I just feel like trucks should come with higher gears like 4.11 or at least make it an option straight from factory which I don't think they do anymore. I understand gas mileage but let the driver control that as much as possible with the right foot. It is a truck after all.

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SGS_Z71 · January 9, 2018

1 hour ago, BamCam said:

My brother has a '17 Sierra and I have a '17 Colorado with the exact same issue. Brother's truck has had the flush done twice and a new torque converter and problem still exists. GM is involved and will be data logging truck this afternoon. His truck is actually worse and almost undriveable at this point.

The more I read posts like this and others I believe his never was trans shudder but a ECM/TCM programming issue (torque management). Our driving styles are very similar and 1/2 our commute is on the same roads, so this may explain why we both have it and not that we are just unlucky. I believe the dealer was too quick to diagnose as shudder and went down the wrong path initially. I too have believed it to be shudder but now I am not convinced my "shudder/chugging" is the infamous trans shudder that is cured with flushing.

I am growing concerned this will never be resolved without 3rd party tuning.

Wow, glad mine isn’t that bad (yet). If you don’t mind, can you please keep me updated? I will do the same. I definitely do not have shudder, sounds like you don’t either.

Glad they are data logging, I asked for the same but it sounds like I have to give my truck to a tech for a period of time to joyride in.

SGS_Z71 · January 9, 2018

28 minutes ago, Bash74 said:

I can say from my experience with my truck before I changed gears the vehicle would have that bogged down feeling almost like trying to start off in 3rd or 4th gear in a manual transmission, but once gear change the truck just felt alive when stepping on gas. Even before I lifted the truck and had a tune it still didn't have the response it does now. I just feel like trucks should come with higher gears like 4.11 or at least make it an option straight from factory which I don't think they do anymore. I understand gas mileage but let the driver control that as much as possible with the right foot. It is a truck after all.

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Leaning towards agreeing 100%

If I trade this in, it will be for a Ford with the 3.73 and 10 speed. Wanted to stick with a push rod V8 though, which is why I chose GM (I am a GM and Ford guy, as I grew up with both sides of the family working in one or the other). I think (thought??) GM makes a better truck though.

Sir Dan · January 10, 2018

Welcome to the "my GM truck 8 speed tranny shifts like ass" club. Love my truck otherwise, it just drives me nuts the way it's always upshifting way too soon which lugs it down and slamming down hard into lower gears sometimes so hard I swear there will be damage.

SILVER SLED · January 10, 2018

There is a tsb for this. I'll look it up tomorrow. The fluid needs to be changed about three times with warm up cycles in between changes. I'll have more details tomorrow.

SGS_Z71 · January 10, 2018

7 hours ago, SILVER SLED said:

There is a tsb for this. I'll look it up tomorrow. The fluid needs to be changed about three times with warm up cycles in between changes. I'll have more details tomorrow.

I looked it up and couldn’t find anything, so I’m all ears. I found exactly what I am describing, but only applies to 6 speeds. Thanks!!

edit - here is the 6 speed one that best describes what I am feeling.

https://gm.oemdtc.com/7877/17249-service-update-chuggle-drive-quality-2017-chevrolet-silverado-gmc-sierra

SGS_Z71 · January 10, 2018

9 hours ago, Sir Dan said:

Welcome to the "my GM truck 8 speed tranny shifts like ass" club. Love my truck otherwise, it just drives me nuts the way it's always upshifting way too soon which lugs it down and slamming down hard into lower gears sometimes so hard I swear there will be damage.

Overall, I’m happy with how it shifts, but definitely notice the harsh downshifts. I guess I’m used to that as my 14’ Sierra 6 speed banged and clunked so much, lol. Little 4.3 never chuggled though, even when towing 7000 lbs. Up to a v8 and now I chuggle. BS.