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

4emeryj44 · June 1, 2016

Thank you for all of this info, I have purchased this same truck and have about 700 miles on it. I have followed the break in by keeping it under 55 mph (mostly) and haven't really noticed any harsh shifting up or down. But I am happy to read with some miles on it this is possible, and their is a fix for it.

I am amazed at all the technology these trucks have in them now. This is my first new truck in about 15 years. I love the styling of the GMC vs Chevy. I am happy with all the tech gadgets and comforts, but still remains a truck.

I completely agree with you, these trucks are amazing in my opinion. This is definitely my DREAM truck, and will be keeping this truck for a very long time. I have absolutely no gripes besides this transmission thing, everything works very well, and it fits my life perfectly. I bought a brand new GMC Sierra in 2004, boy have they come a long way since then.

4emeryj44 · June 1, 2016

On the lower portion of the "B" pillar just above rocker panel is a silver label, build month and year on the top right, e.g. 05/15

SOOOOOOO, 11/15 is my build date. So I need to investigate this a little further. Thank you for pointing that out. Is there a TSB for replacing the older style torque converters if they suspect them to be an issue?

Z45 · June 1, 2016

The new TC replacement is related to 6.2L and 8.sp..

PIE0353

Engineering Information – Shake or Shudder on Light Throttle Acceleration or Steady State Cruise Models: 2016 Chevrolet Silverado Models 2016 GMC Sierra Models Equipped with 8-Speed Automatic Transmission 8L90 (RPO M5U) and 5.3 Engine (RPO L83)

SierraMyst · June 2, 2016

The new TC replacement is related to 6.2L and 8.sp..

PIE0353

Engineering Information Shake or Shudder on Light Throttle Acceleration or Steady State Cruise Models: 2016 Chevrolet Silverado Models 2016 GMC Sierra Models Equipped with 8-Speed Automatic Transmission 8L90 (RPO M5U) and 5.3 Engine (RPO L83)

Where does it say it's 6.2L only?

4emeryj44 · June 2, 2016

The new TC replacement is related to 6.2L and 8.sp..

PIE0353

Engineering Information – Shake or Shudder on Light Throttle Acceleration or Steady State Cruise Models: 2016 Chevrolet Silverado Models 2016 GMC Sierra Models Equipped with 8-Speed Automatic Transmission 8L90 (RPO M5U) and 5.3 Engine (RPO L83)

Regardless, I looked up #PIP5337A: Shake or Shudder On Acceleration Excessive Engine RPM Fluctuation - (Jan 20, 2016) and there is a note in there saying " Note: If the shudder is only present in 4 cylinder mode deem the shudder concern normal characteristic of AFM." So I drove it to make sure and just confirm, but yes this is pretty much the case for me, it only happens with 4 cylinder AFM mode, so it's just tuning of the AFM, which I'm sure they'll get an update for eventually, but at least I know it's not related to TC issue, at least as far as the shuddering goes.

Where does it say it's 6.2L only?

Yeah not sure either, and am wondering this myself. Regardless I did find out more info on the TC issue as I mentioned above.

Z45 · June 2, 2016

Its says right on the PIP 5337C TSB

SierraMyst · June 2, 2016

Its says right on the PIP 5337C TSB

Ahh... You have an updated TSB. It says March 20.

The second revision I had was from January. It's was the revision that added 2016 8 speeds.

I gave it to my dealer and they said it didn't apply to the 5.3L. I couldn't find where they were seeing that. But obviously, they had an updated copy.

4emeryj44 · June 2, 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.

4emeryj44 · June 6, 2016

So I dropped off my truck this morning at the dealership, we will see what comes about. I can tell you, the rental vehicle they gave me is a 2016 GMC Sierra CC 2wd with only 1,300 miles on it, and wow did it shift beautifully. It's hard to believe that's the truck that I purchased and how it used to drive, and now it shifts like a clunky tank. It's just crazy how different it is when it's "new" even though my truck is still new I only have 12,000 miles on it.

4emeryj44 · June 6, 2016

****UPDATE****

So, just called the dealership and got an update on the truck. I truly believe that the route I took with contacting the individual that I found on this forum to contact with GM was the correct route to go. Since talking with the executive liaison, and them dealing with the dealer along with GM technical assistance, things have gone much better than I could have predicted. So now that you know my viewpoint on this, I can proceed. They called GM technical assistance, and were told to replace the transmission valve body along with the Transmission Control Module, which I fully agree with, especially after driving the rental truck and seeing how massively different it shifts compared to mine. I believe it was part mechanical and part tuning with the TCM. So I completely agree with what they are doing. the parts are already on order, be here in about 3 days, so that will be Thursday, I'm hoping it wont take them more than a day, so I should have my truck by next weekend. I truly love me truck, and really hope this fixes the problem. I'd rather not go down the road of a buy back honestly. I also hope this thread will help someone in the future with similar issues.

mookdoc6 · June 7, 2016

Sounds good and I think the route you took was correct also! PLEASE POST BACK AND LET US KNOW WHAT SHAKES OUT!

Bart961 · June 7, 2016

Having this exact same issue, who did you contact at GM? I could use some help. Thanks!

4emeryj44 · June 7, 2016

Sounds good and I think the route you took was correct also! PLEASE POST BACK AND LET US KNOW WHAT SHAKES OUT!

Thank you I appreciate that. I feel as though I've been very patient with this whole process, and honestly I'm very happy with GM so far and the dealership in the way they've handled everything. We will see how it all turns out. I definitely will be posting the results of the valve body and the TCM.

4emeryj44 · June 7, 2016

Having this exact same issue, who did you contact at GM? I could use some help. Thanks!

PM sent! if you need anything please ask. That's the reason for these forums is for us to help each other out on these types of matters. I wouldn't say I'm an expert, but I've experience enough to know the correct way to deal with this process. Everyone's truck is different, but the route I took with contacting who I contacted I believe was a very good route, and it's worked out so far.