My own 8 speed problems & resolution

[huntr1117]

I have a 2017 GMC Sierra with the 6.2 8 speed tranny... Love the truck, but I get a TERRIBLE 3-1 downshift almost every single time i'm coming to a gradual/slow stop. It literally clunks loud and surges my truck forward. It's EXTREMELY frustrating. Bought the damn thing brand new back in October last year. 
 
The dealership has checked the ECM/TCM software and both are up to date. They also performed a transmission 'fast relearn' at the 5k mile mark when they did my first service. I'm at 7k miles and the clunk is STILL there. 
 
My question to you kind folks... Does a transmission flush/filter have the potential to FIX my issue? The service guy said they only normally do that for the shuddering issue some people have, not a shifting clunk.
 
At this point i'm getting pretty desperate to fix this issue... Thanks for any input you guys have!

I pretty much had the same issues with my 17 6.2. I took it into the dealer a few times and they updated the ecm/tcm, and did the fast relearn. Clunk came back about a week later each time. Brought it in again and they did the same thing but also went ahead and flushed the trans. It made a huge difference. Now I'm not positive that the flush is what made it better, but that's the only difference. It's not 100 % fixed. I will still get a random hard downshift but rare now. I figure that once my warranty is up I'll get Blackbear to tune it, but for now I'm fine with it. I'm at 26k miles now so it wont be long. I'd definitely have the dealer do the trans flush/filter.

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[wlezel]

47 minutes ago, huntr1117 said:

 

 

I pretty much had the same issues with my 17 6.2. I took it into the dealer a few times and they updated the ecm/tcm, and did the fast relearn. Clunk came back about a week later each time. Brought it in again and they did the same thing but also went ahead and flushed the trans. It made a huge difference. Now I'm not positive that the flush is what made it better, but that's the only difference. It's not 100 % fixed. I will still get a random hard downshift but rare now. I figure that once my warranty is up I'll get Blackbear to tune it, but for now I'm fine with it. I'm at 26k miles now so it wont be long. I'd definitely have the dealer do the trans flush/filter.

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Did they do a transmission fast relearn for a second time during the same visit they flushed the trans? 

 

Thanks for the feedback @huntr1117 !!!

[wlezel]

@huntr1117 

 

Oh and also... Our transmission is NOT tuneable using ANY handheld tuner. I've already had Diablew custom tune my engine (using a Diablosport tuner), but our TCM's are not tuneable by Blackbear nor Diablosport or any other handheld's out there. Trust me, I would have been all over that already If i could be, warranty be damned. 

 

The 2016 and prior 8 speed trannys ARE tuneable, just not 2017-2018+

 

We are stuck with it. 

[Black02Silverado]

I just read online that the new 2019 trucks coming out and have the 8sp transmissions are having a new updated torque converter in them along some other new hardware. This is in light of all the previous issues and hope to stop it from happening with the 2019's.

[huntr1117]

Did they do a transmission fast relearn for a second time during the same visit they flushed the trans? 
 
Thanks for the feedback [mention=54656]huntr1117[/mention] !!!

Yes they did the fast relearn. They told me that they are supposed to do it anytime they update the tcm.

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[huntr1117]

[mention=54656]huntr1117[/mention] 
 
Oh and also... Our transmission is NOT tuneable using ANY handheld tuner. I've already had Diablew custom tune my engine (using a Diablosport tuner), but our TCM's are not tuneable by Blackbear nor Diablosport or any other handheld's out there. Trust me, I would have been all over that already If i could be, warranty be damned. 
 
The 2016 and prior 8 speed trannys ARE tuneable, just not 2017-2018+ [emoji20]
 
We are stuck with it. 

You can tune the 2017 8 speed trans. I know 2017 8 speed tcms can be unlocked when sent off to hp tuners. Then a tuner that uses hp tuners can tune it in person. I've read of other tuners that have some work around but I dont know the details on it. I've also seen that trifecta performance can tune the trans too. There's a couple of reviews on other posts about it. Blackbear can also tune the 2017 trans. That's who I'm having tune mine when I pull the trigger. Email blackbear and ask them how to get yours tuned or PM me and I'll give you details.

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[SierraHD17]

Haha. My 15 8 speed was the same thing.  Out of the truck multiple times for clunking, delayed engagement, shudders and whatever else.  I tuned the truck which honestly did nothing leading to it's a hydraulic or hard part issue.  Service manager told me the same thing as the guy that started the thread... there was nothing they could do and I was to live with it as GM said they were not going any further on the 15s lol.  I made the best decision of my life and sold the heap.  Problem solved.

[MaverickZ71]

On 3/12/2018 at 2:07 AM, benelli said:

Look at earlier posts. Gm hides behind  there known issues. They make customers come in they claim to do a relearn on the trans which is not the problem and is a waste of time. customer comes in they say  they tried something. customer leaves same thing. unless your retired and have nothing to do all day you would have to take your truck in to them once a week and they still wont fix anything. why don`t they just admit to customers that they screwed up on this transmission. when i told my dealership i was trading this in there response was oh maybe you can trade it in for our 2019 it has a 10 speed. LOL. I told them are you f***ing crazy. you cant even get this one right.

THIS.  They did the same crap to us 07-13 1500 owners on the AFM oil usage problems and all of the other stuff.  First they deny there are any problems, and then they implement a silly multi-phased testing program to weed out the women or weak-willed owners until they are out of warranty.  Never fix the problem, just move on to the next generation.  Oh your vehicle has a problem, well lets just trade for this shiny new one over here!  They never worked out the rough 1-2 shifts on our 6L80E's, but then they were on to making 8 speeds.  Problems with 8 speeds?  So we'll make a 10 speed!  They should be up to their asses in class-action lawsuits!!  But the Earnhardt-tattooed crowd on here will argue forever that all other makes are junk and deny that there was ever a problem with any GM product.    

[MaverickZ71]

On 3/21/2018 at 2:03 AM, HondaHawkGT said:

 

Stuff like relearns, reflashing, software updates, etc are the standard way EVERY manufacturer handles customer complaints. It's been the standard procedure for years. 3rd gen Toyota Tacoma transmission flared shifts/lugging/shift hesitation/clunking shifts? Reflashes and software updates with little improvement. Ram 1500 8-speeds that develop complaints for slipping/clunking shifts/surging/flared shifts: software updates and check fluid levels with little to no improvement. Others were told "it's normal" or "no problem found". The F-150 10-speed has had all kinds of problems: grinding noises, rattling noises, knocking noises, "honking" hydraulic noises, hard shifts, clunky shifts, TCC shuddering, limp mode problems, trans pump failures, electrical glitches etc. Software updates, relearns, "It's normal", etc. No matter what brand you chose, you're going to have teething issues with new transmissions. Deal with it.

So the NEXT time GM goes bankrupt and comes crying to the US Government with their hands out, we will gladly say DEAL WITH IT and slam the door shut!

[wlezel]

4 hours ago, Black02Silverado said:

I just read online that the new 2019 trucks coming out and have the 8sp transmissions are having a new updated torque converter in them along some other new hardware. This is in light of all the previous issues and hope to stop it from happening with the 2019's.

Do you have a link to this? I’d like to check it out!

[wlezel]

3 hours ago, huntr1117 said:

You can tune the 2017 8 speed trans. I know 2017 8 speed tcms can be unlocked when sent off to hp tuners. Then a tuner that uses hp tuners can tune it in person. I've read of other tuners that have some work around but I dont know the details on it. I've also seen that trifecta performance can tune the trans too. There's a couple of reviews on other posts about it. Blackbear can also tune the 2017 trans. That's who I'm having tune mine when I pull the trigger. Email blackbear and ask them how to get yours tuned or PM me and I'll give you details.

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I know you can have the TCM physically changed so it can be tuned, but how does Blackbear do it then? 

[Mileguru]

1 hour ago, wlezel said:

I know you can have the TCM physically changed so it can be tuned, but how does Blackbear do it then? 

Anyone can tune a 2016 and below 8-speed. It can be tuned with HP Tuners or EFILive (i.e. Autocal, i.e. Blackbear)

 

If you have a 2017+ 8-speed, you have to remove the TCM from your truck, mail it to HP Tuners with $200 to have it unlocked, reinstall the TCM, then you can have it tuned by someone that uses HP Tuners software. They will charge you a MINIMUM of $200 to tune it because it costs $200 in HP Tuners credits just to tune it. In other words, if someone chargers you $200 to tune it after you had HPT unlock it, they are doing the tuning for free because they are only charging you the $200 for the 4 credits that HPT requires to tune the TCM (so this scenario is not going to happen). What will happen is you will pay HPT $200 to unlock the 2017+ TCM and then pay a tuner $200 plus his tuning fee on top of that. Of curse if you own your own HPT handheld with GM credits, then you can cut into this cost because you can use your own credits and not the tuner's.

 

It is true that Trifecta can tune the 2017+ TCM without removing the TCM.

 

Blackbear has CLAIMED to be able to do the following, but it did not work on my truck when they tried it:

1) Mail you a 2015-2016 TCM

2) Remove your 2017 TCM and swap in the 2015-2016 TCM

3) Flash the new TCM with a tune

4) You now have a 2017 8-speed truck that has a tuned TCM

But again, it didn't work for me when they tried it.

 

I hope this helps. Feel free to PM me if you have any questions. I've gone through this entire process from start to finish so I know all of the ins and outs.

[huntr1117]

Blackbear has CLAIMED to be able to do the following, but it did not work on my truck when they tried it:
1) Mail you a 2015-2016 TCM
2) Remove your 2017 TCM and swap in the 2015-2016 TCM
3) Flash the new TCM with a tune
4) You now have a 2017 8-speed truck that has a tuned TCM
But again, it didn't work for me when they tried it.
 
I hope this helps. Feel free to PM me if you have any questions. I've gone through this entire process from start to finish so I know all of the ins and outs.

Could you PM me info on when you went through this with Blackbear? I talked to them last month and they said mine could be tuned as long as I got a spare tcm from a 2015-2016 6.2 8 speed. I picked up a 2016 tcm from an Escalade and they said it would work fine. Only reason I haven't ordered the autocal yet is because I'm waiting to hit 36k miles.

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[Mileguru]

12 minutes ago, huntr1117 said:

 

 

Could you PM me info on when you went through this with Blackbear? I talked to them last month and they said mine could be tuned as long as I got a spare tcm from a 2015-2016 6.2 8 speed. I picked up a 2016 tcm from an Escalade and they said it would work fine. Only reason I haven't ordered the autocal yet is because I'm waiting to hit 36k miles.

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No need to PM you, I can say it here. I tried this process with Blackbear from late May through June. They said it worked with other trucks, but it didn't work with mine. I really wish it had, of course!

[huntr1117]

No need to PM you, I can say it here. I tried this process with Blackbear from late May through June. They said it worked with other trucks, but it didn't work with mine. I really wish it had, of course!

What tcm did you use? What was the doner vehicle?

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