2016 GMC Sierra 1500 CC Z71 8L90 2nd to 1st downshift issues

intimidator01238 · June 8, 2016

Yeah so a GM executive liaison contacted me today because I emailed someone that was mentioned to email on this forum. They contacted my local dealership today and they want me to come in next week for this transmission issue. The shuddering issue they mentioned didn't apply to my truck obviously due to it being a 5.3, but again they had the updated TSB and I never noticed it was for the 6.2 only. Anyways, so the plan now is to take it back into the dealer for the hard shifting 1-2-1 gear shift and then the tech will be I contact with gm technical assistance and go from there. This in my opinion will be GM's last attempt to fix this issue. I've been a good and fair consumer, I've dealt with this issue multiple times with no results. If I receive the truck back with the same issue, it's time for a buy back.

Who did you contact at GM?

4emeryj44 · June 8, 2016

I had emailed a mary barra, but received a phone call from someone else but it was on her behalf.

4emeryj44 · June 8, 2016

****UPDATE****

So the Dealership called me today to inform me that they changed out the valve body and TCM and the truck still wasn't any better. They ordered a whole brand new transmission first thing this morning. I was not expecting that at all to be honest. They said it will take a few days to get here, so I'm hoping by middle of next week she'll be up and running.

mookdoc6 · June 9, 2016

Good to hear! It's coming to a close now for you and man you gonna love the smoothness!

GM has and does stand behind their products!

FADEC · June 10, 2016

I'm also interested in the outcome of this thread. My 8 speed 5.3 is also quite clunky and harsh most of the time. I can deal with the harsh shifts but what I cannot deal with is that when slowing down for a stop sign, right when coming to a stop is the bump or push feeling. Those who have it know what I'm talking about. They did the relearn, no change.

f8l vnm · June 10, 2016

The famous clunk has been here for years and not going away. My 08 had it my 14 had it and now my 16 has it

Denali62 · June 10, 2016

My truck had the same issues including a tcc that would constantly engage and disengage causing a shudder(reminded me of a 1st gen 700r4 w a lot of miles on it lol

Mary Barra is who you all want to deal with. My truck was fixed without replacing or reflashing(aside from the 15389) update. All it took was for the tech to run two consecutive transmission flushes. My tc and trans act 100% normal now. I'm assuming there were either some metal trash or maybe the clutch faces were not true and cause a lot of particulates early on? Causing the orfice from the tccs to be partially blocked, which allowed the tc to slip more than the pwm 100 rpm.

I know lots of acronyms hahahahaha

Jimmyc! · June 15, 2016

I'm still having the issue even after the re-learn. I thought I was onto something when I read about shutting off grade braking ~ better but not much. I'll just have to keep hammering at my dealer and who knows. Maybe it is just a trans flush. About this Mary Barra. How do I get a hold of her?

4emeryj44 · June 15, 2016

[email protected], but she'll most likely pass it off to someone who will still handle your case and scenario and get things handled the way they should.

They are pretty much just going to be a liaison in a sense between you and the dealer. Just a little added pressure from the top makes a difference

SierraMyst · June 15, 2016

My truck had the same issues including a tcc that would constantly engage and disengage causing a shudder(reminded me of a 1st gen 700r4 w a lot of miles on it lol

Mary Barra is who you all want to deal with. My truck was fixed without replacing or reflashing(aside from the 15389) update. All it took was for the tech to run two consecutive transmission flushes. My tc and trans act 100% normal now. I'm assuming there were either some metal trash or maybe the clutch faces were not true and cause a lot of particulates early on? Causing the orfice from the tccs to be partially blocked, which allowed the tc to slip more than the pwm 100 rpm.

I know lots of acronyms hahahahaha

I had asked about the double flush to correct my issue and was told it's only for 6.2L.

Is yours a 6.2 or 5.3?

Denali62 · June 15, 2016

It is a 6.2 8l90. I wouldn't have neither the 5.3 or the 6l..whatever it is...

Not being a snob just saying I have driven both and the 5.3+6speed feels like my dads old 3.9 Dakota after driving my truck.

4emeryj44 · June 18, 2016

****UPDATE****

Alright, I received my truck back form the dealership with the new transmission a couple of days ago, I wanted to drive it around and get a feel for if it was fixed or not before I posted. SO! I had first pulled it out of the dealership, tried to duplicate what it was doing prior, it hickuped a little at first, but NOWHERE NEAR what It did before, I was hesitant. I decided to just take it home and give it some good time and some good mileage before I had made up in my mind to take it back. Since then, everything has been smooth as butter, just like when I originally bought the truck. I am worried though that it's driving so well like it did originally but then everything will go back to crap after a few thousand miles, but I can't think like that because she's diving beautifully right now and I'm loving it. The 1-2-1 downshift seems to be just fine now. So, I have all the documentation just incase obviously, but they did replace the transmission and new torque converter. The original xfer case obviously and TCM are in the truck.

Like I said, I'm going to give it at least a couple thousand miles and see how she does. For now, seems like she's all fixed up and running good. I had a 2WD Sierra as a loaner, and idk if it's just me, but my truck seems peppier and more responsive than that truck and from before. IDK if it's because it's in the new mode of driving, or if they maybe gave the TCM some better parameters or what, but she runs WWAAAAYYYY better. I'd like to thank the Executive Liaison I was dealing with, the Dealership, I think everyone including GM handled everything very well, and I got my truck back quicker than I expected.

SierraMyst · June 19, 2016

****UPDATE****

Alright, I received my truck back form the dealership with the new transmission a couple of days ago, I wanted to drive it around and get a feel for if it was fixed or not before I posted. SO! I had first pulled it out of the dealership, tried to duplicate what it was doing prior, it hickuped a little at first, but NOWHERE NEAR what It did before, I was hesitant. I decided to just take it home and give it some good time and some good mileage before I had made up in my mind to take it back. Since then, everything has been smooth as butter, just like when I originally bought the truck. I am worried though that it's driving so well like it did originally but then everything will go back to crap after a few thousand miles, but I can't think like that because she's diving beautifully right now and I'm loving it. The 1-2-1 downshift seems to be just fine now. So, I have all the documentation just incase obviously, but they did replace the transmission and new torque converter. The original xfer case obviously and TCM are in the truck.

Like I said, I'm going to give it at least a couple thousand miles and see how she does. For now, seems like she's all fixed up and running good. I had a 2WD Sierra as a loaner, and idk if it's just me, but my truck seems peppier and more responsive than that truck and from before. IDK if it's because it's in the new mode of driving, or if they maybe gave the TCM some better parameters or what, but she runs WWAAAAYYYY better. I'd like to thank the Executive Liaison I was dealing with, the Dealership, I think everyone including GM handled everything very well, and I got my truck back quicker than I expected.

I also have 5.3 and I'm going to inform them on the initial oil change about my clunky 1 to 2 to 1. Hopefully, they'll attempt to fix it. Hopefully, they won't say it's normal like always.

4emeryj44 · June 19, 2016

I also have 5.3 and I'm going to inform them on the initial oil change about my clunky 1 to 2 to 1. Hopefully, they'll attempt to fix it. Hopefully, they won't say it's normal like always.

Well since you kind of know what it possibly could be, you can always print all this info I've posted and make a case to see if they will expedite trying to actually fix it versus calling it "normal" because now we know it's not normal. Now you know when the relearn doesn't work, and the adaptive fast learn transmission procedures don't work, and the valve body and TCM don't work, its the transmission with a new torque converter. That way you don't take it in the first day and the relearn it and give it back, then the next trip they do the next thing and give it back. Don't accept the truck back until they drive it and make sure it's fixed.

mookdoc6 · June 19, 2016

Awesome! It's unfortunate but anyone of us on this forum could have gotten that bad Tranny! The important thing is you went about it correctly and level headed. My experience has been....GM backs their products much more than the other manufactures and always have! Which means the dealership will go out of their way to fix problem for you. I dare any of you to go play these games with Fiat/Chrysler on something like this.

Give it some time the normal herky/jerky will be there for 1500 miles at least! And then POOF! you will not be analyzing every freaking shift point and trying to recreate the same jerkness around this corner at this speed ETC. You will be driving it and thinking WOW it's gone this thing is smooth? I can't even feel it shift WTF? Glad you got the butterness now BRO!

Thanks for Posting again so others can follow the outcome etc!