8 speed trans, reprogram

Crobinson16 · November 23, 2017

So are these tabs applicable to 2017 6.2 with 8spd?

SandyNeck · November 23, 2017

Hey Guys,

I have a 2017 with the 6.2L and 8 speed. I was occasionally experiencing moderately rough shifts from 1st into 2nd, especially when the truck was cold. When I would pull out of the driveway onto the street in the morning, it would sometimes slam into gear at around 8 MPH under light acceleration. The problem wasn't severe, just an annoyance. Anyway, I recently had it in for service (grease, oil, filter, tire rotation) and asked them to check if there was an update available for the transmission while it was there. When I picked it up, they informed that they did install a software update and advised me that it would be relearning for a while.

About half a mile from the dealership, I was stopped at an intersection and waiting for an opening in traffic. When I saw a chance to enter the intersection, I applied the accelerator and experienced hesitation. There was no response to the throttle for about 1 second. The truck then lurched forward and launched me into traffic. It only happened that one time so far, so not sure if it was a temporary problem from the reprogram, or an intermittant condition that might occur again. I haven't noticed the rough shift since the update, but it's too early to tell. I'd rather put up with the rough shift than the hesitation, as the hesitation could be dangerous. Reading through this discussion, it appears that others have had similar experiences.

Iceman22 · November 23, 2017

I wouldn’t be too worried about it unless it becomes a reoccurring issue. I had my relearn done a couple months ago and the service advisor went out of his way to tell me “the truck will be learning your driving style over the next couple days. Don’t be alarmed as there could be times that the tranny will feel like it’s damn well going to fall out of the truck”

There was a couple random weird moments over the first two days and then everything settled in. The relearn completely cured my delay from park to drive on cold starts and my occasional jerky 2 to 1 shifts

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LFZ · November 30, 2017

I took my truck to get the reprogram done, and they didn't do it because they said their tech couldn't replicate the problem during his test drives. My stealership also sucks too....so just FYI.

My clunky 8 speed seems to only happen on occasion, mostly during the first few shifts from a stop, but apparently wasn't enough for them to do the work.

Bunks · December 1, 2017

On 11/30/2017 at 1:23 PM, LFZ said:

I took my truck to get the reprogram done, and they didn't do it because they said their tech couldn't replicate the problem during his test drives. My stealership also sucks too....so just FYI.

My clunky 8 speed seems to only happen on occasion, mostly during the first few shifts from a stop, but apparently wasn't enough for them to do the work.

I had to tell them "A buddy had this same issue and his dealer did this reprogram and it fixed it. Made a world of difference." (Thanks to my "buddy" GM-Trucks.com)

They didn't bat an eye and did any optional update for the whole truck. They did note on the service invoice that they couldn't get what I was describing to happen but they still did the reprogram.

kevinfranklin · January 17, 2018

I'm a rather conservative driver, and want/expect my vehicles to last for >150k miles. This is my first truck (2017 5.3 4x4 ..... 6speed though), but am surprised and worried about this same transmission "searching" and clunking that make me think I'm wearing down what SHOULD be a smooth tranny. I guess I was hoping it would work or "learn" it's way out, or I'd figure out how to avoid it, but it just concerns me every time I drive around town (1st --> 2nd --> 3rd and then back down are the real culprits). Sounds VERY similar to the symptoms in this discussion.

If ANY kind of a tune (GM or custom) makes the tranny work SMOOTHER, then I'm all in, cost be damned. Although I will get my stealership (love that term) to at least attempt to fix it. I want a comfortable, smooth ride that at least gives me the impression it's going to last a long time.

Have any other "conservative" 6 speed drivers out there seen the vast improvement after either a GM or a custom tune???

Crstfr · January 17, 2018

On 11/30/2017 at 1:23 PM, LFZ said:

I took my truck to get the reprogram done, and they didn't do it because they said their tech couldn't replicate the problem during his test drives. My stealership also sucks too....so just FYI.

My clunky 8 speed seems to only happen on occasion, mostly during the first few shifts from a stop, but apparently wasn't enough for them to do the work.

mine did the same.. i' m like.. you drive it for 10 mins.. after warm... .. i drive it everyday~... . .i'll be taking it back.

michigan2500hd · March 19, 2018

Taking my 2015 8 speed in this week for Warranty work including the trans. Typical sloppy shifting but the big issues are..
1. Trans doesn't want to downshift into first or second even if I say come up to a red light and it changes to green while I'm coasting a couple or few mph. Bogs down and either takes off slow or finally downshifts with enough throttle input and you look like your trying to race.
This even happens in tow/haul mode which makes for dangerous and uncomfortable trailering.

2. The 2-3 shift is really soft and takes forever. But the time it settled in it's going into the next gear. Weird feeling and sounds terrible.
Anyone else experience these issues??

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.justin. · March 19, 2018

On 11/9/2017 at 6:43 PM, chrispassas21 said:

If someone that has a 5.3L 6 speed transmission and did something like this please let us know. I️ am having problems downshifting either from 3-2 or 2-1 I️ get the clunk a good amount since I️ do mostly city driving. Very upset about that.

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All of the 2014+ models have a greater tendency to clunk on a downshift due largely in part to torque converter strategy. Sometimes an update from GM can help improve it, sometimes custom tuning is needed.

You can go to https://tis2web.service.gm.com/tis2web/ and see if there are any software update specific to your truck available by inserting your VIN and selecting the TCM option. It won't list what software version you presently have, but it will list what changes have been made available and for what reason. As I recall, very few, if any, of the 6 speed trucks have updates available from GM leaving custom tuning as your next best choice.

.justin. · March 19, 2018

On 1/17/2018 at 6:44 AM, kevinfranklin said:

I'm a rather conservative driver, and want/expect my vehicles to last for >150k miles. This is my first truck (2017 5.3 4x4 ..... 6speed though), but am surprised and worried about this same transmission "searching" and clunking that make me think I'm wearing down what SHOULD be a smooth tranny. I guess I was hoping it would work or "learn" it's way out, or I'd figure out how to avoid it, but it just concerns me every time I drive around town (1st --> 2nd --> 3rd and then back down are the real culprits). Sounds VERY similar to the symptoms in this discussion.

If ANY kind of a tune (GM or custom) makes the tranny work SMOOTHER, then I'm all in, cost be damned. Although I will get my stealership (love that term) to at least attempt to fix it. I want a comfortable, smooth ride that at least gives me the impression it's going to last a long time.

Have any other "conservative" 6 speed drivers out there seen the vast improvement after either a GM or a custom tune???

3

I tend to prefer to set up vehicles to shift quick and crisp. Not a long slippery shift, not a jarringly firm shudder into the next gear. Get the job done as quickly as possible and move on to the next gear. That would include about 125 2017-2018 trucks to date.

Any tuning has the potential to be harsh or unpredictable upon initial flash, so whatever you go with, I would encourage you to give it a bit of drive time so that the TCM can dial in the adaptive pressure tables.

TRG · March 20, 2018

12 hours ago, .justin. said:

All of the 2014+ models have a greater tendency to clunk on a downshift due largely in part to torque converter strategy. Sometimes an update from GM can help improve it, sometimes custom tuning is needed.

You can go to https://tis2web.service.gm.com/tis2web/ and see if there are any software update specific to your truck available by inserting your VIN and selecting the TCM option. It won't list what software version you presently have, but it will list what changes have been made available and for what reason. As I recall, very few, if any, of the 6 speed trucks have updates available from GM leaving custom tuning as your next best choice.

Thanks for providing that software update link. I plugged in my VIN and did see something pop for a transmission update for the "fishbite" issue, which is exactly what I have. I'm bringing my truck (2018/5.3L/6 spd) back to the dealer this Thursday and will be mentioning that it looks like there may be an update out there to address the issue.

Crobinson16 · March 20, 2018

13 hours ago, .justin. said:

I tend to prefer to set up vehicles to shift quick and crisp. Not a long slippery shift, not a jarringly firm shudder into the next gear. Get the job done as quickly as possible and move on to the next gear. That would include about 125 2017-2018 trucks to date.

Any tuning has the potential to be harsh or unpredictable upon initial flash, so whatever you go with, I would encourage you to give it a bit of drive time so that the TCM can dial in the adaptive pressure tables.

Ok so I checked out the tis web site and it appears there is a update available. Just says for improved shifting, not sure if I already have it or just that its available to my vin. Also with the 17-18 8spd truck's you are only tunning the ecm correct? How does that affect the tcm if it's not being tunned.

Crstfr · March 20, 2018

here's what they did for my 5.3 8sp... its a 2016... ..drives much better... .and gained 2mph per gallon!..

.justin. · March 20, 2018

3 hours ago, TRG said:

Thanks for providing that software update link. I plugged in my VIN and did see something pop for a transmission update for the "fishbite" issue, which is exactly what I have. I'm bringing my truck (2018/5.3L/6 spd) back to the dealer this Thursday and will be mentioning that it looks like there may be an update out there to address the issue.

Good luck!

.justin. · March 20, 2018

2 hours ago, Crobinson16 said:

Ok so I checked out the tis web site and it appears there is a update available. Just says for improved shifting, not sure if I already have it or just that its available to my vin. Also with the 17-18 8spd truck's you are only tunning the ecm correct? How does that affect the tcm if it's not being tunned.

We have successfully tuned a few 2017+ 8 speeds now by swapping to a 2015/2016 T87 TCM. We don't yet offer this as a regular service due to the relatively high cost of those TCMs. If you can get ahold of one yourself, then it is just a slight increase in the AutoCal tune price to cover tuning for it.