2016 Sierra Shifting Problem 6 speeed automatic

I have a little over 4000 miles on my 2016 Sierra Denali. Have had transmission and acceleration issues almost from day one. After switching gas from Regular to Super Unleaded, the acceleration issue cleared up for the most part. However the transmission issue continues. When it shifts from first to second, it hits so hard, I feel like I have been hit by another vehicle. This happens when it down-shifts from second to first but not quite as often as when it goes from first to second. Have had it looked at by the the dealership where I bought the truck but they said they couldn’t find anything wrong with it. They wanted me to leave it overnight but could not find a vehicle to loan me. Haven’t heard anything from them in over a month. Have scheduled another appointment with them to see if they will actually do something about this. They did admit the first time around that they had a bulletin from GM about this issue but it was not yet a recall.

Lots of these complaints fall on deaf ears because its really the programming of the transmission operations. Its all computer controlled and designed to modify itself as its in use. You are driving a computer and its more of the driver who has to learn how to drive it. Sorry, that’s not what you want to hear but i believe its the mindset of the GM engineers who program these transmissions. They have to squeeze as much fuel economy from these engines as possible. If you think the 6-sp and 8-sp are bad, wait till you have to live with a 10-sp.

I own a ’15 silverado and it has about 25,000 on it and still notice those same issues. Low rpm acceleration it shifts to higher gears to soon causing truck to shutter/shake. Then one day I had to slam brakes hard to stop and when I accelerated again, it had never shifted all the way down to first. Sounded like it was in neutral for a minute..of course dealer couldn’t replicate any of it!!!

I have a 2016 Canyon that shifts the same way. I had a 2010 Sierra six speed that had the same issue until the transmission was retuned. So it is possible to fix this problem.

@djlouque Thanks for sharing that. Would you have any other details about the transmission retuning that helped yours?

I purchased HP Tuner many years ago. Worked with several very knowledgeable friends and came up with a much better shifting pattern for the 6 speed. There are several issues doing this such as warranty on your vehicle. The days of putting the stock tune back in undetected when you bring your vehicle to dealer is over. GM should give the consumer the choice of a shifting pattern that is more desirable. I would gladly give up a little bit of gas mileage for a better performing vehicle. My 2016 Canyon is worse than my 2010 Sierra in the shifting department. I use manual shift over 50% of the time. The tuning file is broken up into 2 parts,. the VCM file for the engine and TCM for the transmission. Please GM, fix this problem!!

Thought I would let you know, looking to buy 2016 Chevy Silverado LTZ z71 1500 6.2 , or 2016 GMC Sierra SLT or Denali 1500 6.2 4×4. NOT NOW! Drove a new 2016 LTZ(as above). 6.2 – 8 speed hesitated every time I took off from a start. Was going to drive a GMC(above). Read in the CARCOMPLAINTS.COM – NHTSA – this morning, 2014 – 2016 GM 1500 trucks, vibration. Always been a GM guy. Drove a Crew Cab F 150, 4×4, 3.5 Twin Turbo, my wife and I loved it. Everything about it except price, and now reviews. I hope you guys get everything taken care of on your trucks. GM trucks, in my opinion are great looking trucks! Guess now I will look at GMC CC 2500HD, don’t seem to have many problems. Will keep watching to see if you guys get things taken care of. Good Luck!!

My 2016 Sierra SLE has similar issues. However, I found a temp solution that I’ll continue to use until GM produces a solution (not holding my breath). I purchased an aftermarket mod that plugs in to the OBD port. It does not modify the tune but it disables the AFM feature. The engine never switches from 8 cylinder mode. I have the 5.3L and my gas mileage has not changed in a measurable amount. I drive 100 miles per day round trip in varied city/freeway traffic and I’m seeing 16 – 18 mpg average over 400 miles.

I can confirm that it did not flag on my truck when I took it to the service center last week for the airbag recall service. Before I left home, I unplugged the device, started the truck and drove to the center. This is the procedure detailed in the user info for this mod.

I left it unplugged until the work was done and I was leaving. They never mentioned it and I was in and out in about an hour.

The point is, that without the constant changes to cylinder configuration, the transmission shifts better. I’ve also read that after a few months of of this, you can stop using the mod and let it go back to normal mode with AFM. By this time the transmission has “learned” how to shift. There might be some minor degradation because of AFM but eventually, the transmission computer can compensate for the change in profile and smooth that out too. I cannot personally attest to this however.

g094389 Can you give me more info on the mod you purchased

Just purchased my 2016 Sierra SLE and this is driving crazy. would love to try the mod fix

My 2016 GMC goes to the dealership this Wed. They have all ready had my truck two times over the bad shifting and always say the same thing. They scanned it and can’t find anything wrong. With all the problems so many people are having you know General Motors know they have a problem. But they want do a recall until forced to. The dealership would never let me have a loaner vehicle to drive while checking my truck. I got tired of the Dealership BS. I don’t think they are allowed to tell us what is causing the problem. I called General Motors and the dealership called me in less than 12 hours. This time they are rolling out the red carpet and are going to give me a new Silverado to drive until they fix my problem Don’t let the dealer jerk you around call GM. If we don’t all speak up it will never be fixed. If they don’t fix my truck I’m going for the lemon law and make them refund my money and take the truck back. I have one advantage over most of you. My transmission just stopping working at about 30 mph. It shifted out of high gear but did not go into the lower gear. My engine revved up like it was in neutral. I stopped the truck in the middle of the street because I had no place to pull off. Motor still revving up. I put it in park turned off the key then restarted the tuck it was OK until next time. If it did that while merging onto a freeway I could have been killed.

2016 3500 HD 6.0L 6 spd, SRW 4×4, I don’t have any issues with the truck so far as not shifting; in my case the shifts are super smooth but I find that if a cricket farts in the ditch the transmission downshifts. The fuel economy (lack thereoff) seems to be related to all the shifting so that even on a level road it wants to downshift for no reason. I have 7400km (4625m) so I am hopeful that the fuel economy will increase some and the transmission will learn to stay in one gear most of the time.

I am looking into buying a programmer (banks) to load either the 87 sport or the 91 sport mode in and see if this changes the shift pattern and fuel economy? Anyone have any real data on using a programmer and what were your results?

I know that the programmer will reflash the ECM which could affect warranty but I will deal with that issue later if it comes up. I am aware of the custom tunes available including EFIlive and am not interested in purchasing any of them. I am also aware that I can use the manual mode to hold gears longer but I am not a drag racer and do not tow any heavy loads.

My last truck was a 2009 LMM Dually and with the programmer on 3 it never shifted on the highway; was very responsive and had about the same fuel economy as stock.

If GM can’t get a six speed gas combo programmed to work correctly, why bother to make an 8 speed or 10 speed go back to the 3 speed with overdrive????

Purchased a 2017 (but made in late 2016… never understood that) SLT 1500 2wd about a month ago. It’s at the dealer now, for the the 3rd time for the same issue, which is the lack of smooth acceleration / shifting issue that everyone’s describing here. The first time, they updated the computer. …no difference. Second time, they adjusted a “road force issue” …which I’ve come to learn, means they balanced the tires. …no difference. …but now it has a shimmy that wasn’t there before, that at 70mph will rattle the teeth out of your head, and even Discount Tire (on my own dime) can’t seem to get it fixed. FML! Each time, they’ve put me in a loaner truck that doesn’t have this issue, so I know it’s not just me… especially after reading these posts. But, I can’t duplicate the problem effectively for their techs, so they’re about to wash their hands of me and my “problem” that apparently only I can see/feel.

I realize the post was from last October, but if anyone knows what mod ‘g094389’ was speaking of (from Oct. 11 2016 at 1:44pm) in the post above, I’d be interested in taking a look at something like that. I have a feeling I’m about to be ‘on my own’ with this issue, and I don’t have a clue what to do about it, but I do know that for what they’re charging for a new truck these days, I expect it to shift properly, at least. It’s a shame, too. I love everything else about the truck.

I do agree with the idea that GM has to know this is an issue, but my dealership acts as if they’ve never heard of this before. Does anyone know of any updates, fixes or solutions of any kind for this issue, or any suggestions for a course of action? Do I have a leg to stand on for a ‘lemon law’ case? Any help is appreciated.

I believe the mod g094389 was talking about is the Range Technology AFM delete (https://rangetechnology.com/afm-disabler/). It plugs into the OBD port and block the signal telling your engine to drop to 4 cylinders. No ecm or tcm programming, so warranty is safe(r). I purchased this device to try and clean up the clunking during the “learning stage” as my 2016 Silverado LTZ Z71 couldn’t balance the changing cylinders and 6-speed tranny for a comfortable ride. The clunking went away on its own, but I still keep the afm delete plugged in as I have a borla exhaust and the changes in sound going in-and-out of V4 mode drove me nuts.

The bad news is that the AFM delete is NOT going to solve any of the drivability problems listed here. These are all intentionally programmed into the transmission to meet CAFE requirements (mpg) and extend the life of the transmission via torque management. The only way you can fix this is with 1) Trade-In or 2) Tune, which will void warranty. This is usually the part where people say you can return to stock tune before going to the dealership or point you to the Magnuson–Moss Warranty Act. Either way, your money, do what you wish.

Just wanted to let you guys know. I did order a 2018 GMC 2500HD Denali. Got it about a month ago. Now has 2200 miles on it. Red Quartz Tintcoat. Cocoa dune interior, 6.0 gas. I ABSOLUTELY LOVE, my truck!

I have same issue as other posts. Purchased a 2017 Sierra Denali 6.2 L 8 speed. Shifting from 1st to 2nd has a short delay and then a hard shift with loud clunk/bang. Doesn’t happen all the time, but when it does I cringe thinking I’ve left parts behind on the road. At my first service, I mentioned it to the dealership (guys at my dealership are pretty attentive). I was told it is a common issue and normal for the 8 speed transmission. Seemed to me it got worse and more frequent, so I brought it back to the dealership. They had it all day and couldn’t replicate the problem. They are keeping it overnight and will try cold in the AM. In the meantime, I’ll drive my 2008 Chevy that shifts smooth as silk!!!!!! Seems like a real solution is in order?

I also own a 2016 GMC SIERRA and the dang truck has the same issue at about 20 to 30 miles per hour when I’m in stop and go traffic.
Sometimes it makes a terrible clunk sound as if the drive shafts is falling off.
I also called GMC dealership and they told me the same thing that my truck needs to learn my driving habits.
Too bad because we really like this truck.

has anyone had any progress with this issue? I have a 2015 V6 and took it in for this issue after its first oil change. they said it was operating normally. I don’t want to chip it and void its warranty but I can’t stand it.

My 2014 Sierra SLE 4×4 crew cab (5.3l, bought new in late 2014) went through the “clunk” phase as it was supposedly “learning” (yeah, right) my driving habits. During the “clunk” phase, whenever my coworkers would ride with me, they would inevitably ask “What’s wrong with this truck?” as it slammed and jerked. Now, with 41K miles, it doesn’t clunk anymore, but it drops into 4 cylinder mode at the slightest lift of your foot on the accelerator. When driving below about 45 mph, it will lurch into 4 cylinder mode, lug for a second or so, and then lurch back into 8 cylinder mode. It’s fine above 45 mph. I have asked the dealer repeatedly to reset the system back to the way it was when it was new, but they say there is nothing they can do about it. If they can find a way to reset it before I get sick of driving it, I might consider another GM truck. Otherwise, I will find something else.

I have a 2014 GMC Sierra 1500 5.3L 6 speed. At 89k miles, I brought it back to GMC for some major transmission issues. A week after buying this truck new I took it to GMC for the shifting but was told that was normal… well at 89k miles they replaced a couple valves as well as the torque converter. Unfortunately that did not solve all my problems. One night when my tranny was acting up the check engine light began flashing. Now I don’t know anything about trucks but when I brought it back to GMC at 92k miles they instantly looked into getting approval for a new transmission. To me, that sounds like this is a common issue and these reviews tell me that as well. So today I pick the truck up and see how it is with a remanufactured transmission with another 100k mile warranty. My advice to everyone would be to push GMC to look into those issues for you and don’t buy another GM truck. I learned my lesson. Will add that my loaner (2019 GMC Canyon v6 8 speed) shifts much nicer but still not like a ford…

Hi,
I have a 2014 GMC Denali and have had exactly the same problem you’ve are talking about.. Yesterday I put my Vehicle in to have it checked out at the Australian dealership for GMC. They did updates on the PCM, GLO Plug module and TCM as I kept on getting Code P2202 which involved the Nox circuit.
Next they did a software update on the Transmission and fixed the Clunky problem. It now changes as smooth as and could not be happier with the result.
The people I took it too were Performax Australia in Northlakes Qld.

Take it a dealer the very first time you notice any problem at all. This establishes the starting mileage of problem reporting, and should the problem be un-fixable like 8L90 and 8L45 transmission problems, when you get to the point of filing for buyback or vehicle replacement, this mileage point will be used in calculating the amount you get back or the amount you can apply to vehicle replacement.

I have 2015 8 Speed Sierra Denali and it has same problem, when it shifts down sometimes there is a hug hit from back like other car hits you from back, I sent the truck to the dealer and they recommended to change the transmission heat fluid sensor, then the harness but without any benifit, After that they recommended to open the transmission and change the transmission discks.
I have changed all discks as they recommended but no thinge changed, Then they checked the programming and the throttles.

Finally, they admits after all this money lost that it is a common issue is some trucks and they call it clutch bumb from back and there is no thing to do.