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My 8-speed Auto Transmission is a Stumbling Drunk

InVision

By InVision
in Engines & Drivetrain

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InVision Enthusiast

InVision

Posted
  • Author
Posted

NO help here.  put our name in to class action suite hat.

 

M

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midwestdenaliguy Enthusiast

midwestdenaliguy

Posted
Posted

So here's been my recent experience, it seems there is no one-size fits all fix for this issue but mine is now good. I have confidence in my truck again.

 

I've got a 2016 6.2L Denali, crew cab short bed, with the 8-speed that I bought used with 50k miles. Shifted and operated smoothly up until around 75k miles when I had the transmission fluid replaced (as part of maintenance). After the flush, I noticed the dreaded shutter when lightly accelerating the truck under load (going uphill on the highway). It was noticeable, but not bad and it didn't happen for another week or so. Thought it was a one time fluke until it happened again, then every day I would notice it when the engine was under load. I also noticed when driving it with a cold transmission, the shift from 2nd to 3rd was hard and felt like it slammed into place if I was really on the accelerator. Also, if I started the truck while cold and shifted it into drive or reverse soon after, sometimes the engine would do a high rev and want to launch the truck. Both the shutter and hard shift slowly got worse over the next few weeks. Then I towed a 1,000 pound trailer with a 750 pound ATV and it got really bad - shutters that made me lunge forward in my seat. Called the dealership and told them something was not right after my tranny flush. The service director handled my case directly and didn't even test drive it, took my word for it. He told me they've had a number of the 8-speeds come in with the issue - Silverado's, Sierra's, and Corvette's. They did a triple flush cleaning of the trans, replaced the TC, put in the new fluid, and reprogrammed the transmission. Even though I was out of my powertrain warranty (5 year/60k mile), they covered all the cost and filed it under 'customer loyalty'.

 

I noticed right away the reprogramming helped with the shifting. No more hard shift, no more high rev when putting it into gear right away on a cold start, and no shutter...for the first few days. After having it for about 5 days I noticed the shutter coming back. I thought here we go again. Then it had one really bad day of shuttering worse than it had done before. Next day it was gone and never came back. What?!? That was about 13k miles ago and it has been smooth the entire time (repairs done around 78k and now I'm at 91k). I don't understand it. I'm guessing the new fluid and TC needed a few hundred miles to 'break in' or there was a little old fluid left that got worked out?!? 

 

Just towed 3k pounds 500 miles and didn't have a single shutter or hard shift. The truck has seen highway, rolling hills, gravel roads, two tracks in the woods, and mud. No shutters or awkward shifts. I'm curious, has anyone had a similar experience as me where after the repairs it had one final flare up then went away?

InVision Enthusiast

InVision

Posted
  • Author
Posted

Congrats.  Class action suit is for 5.3L - 8 Speed Transmission...

 

M

mrwarrior737 New Member

mrwarrior737

Posted
Posted

I have a 14 with 6.2 with 6 speed and tow pack.

Terrible trans issues with it stumbling all over it self. Even makes a slack noise when you are on and off the gas... I cant tell if its in the transfer case or transmission.

I have been to the dealer multiple times.

Last 2 times I got charged 120$ inspection fee and they still found nothing.

I have been handed a bulliten 2 times about transmission clunk and slack noise.

 They cant fix the high speed shutter. Claim everything is within specs.

Monday it was to the dealer and 40  miles later on the odometer the tech claims he found nothing, nothing at all. Everything was good to go.

I have 2 friends with the truck almost exact build, motor and trans, Which do not make this noise or have a shutter or stumbling trans at low speeds

I can let off the gas and get back on it and recreate this sound while driving every day.

Like a slack isse somewhere in the system.

 

I attached a video if the sounds. It stumbles through the gears as will.

 

 I have 2 videos on this already and the dealer cannot help.

 My truck is still under warranty for another 5k until I roll 60k. I feel like they are waiting me out to run out of warranty but I explanined ot the prick 3 times I paid for a 84 moth 100 k extended and supplied my documents.

 

I am on my last nerve wit the truck. Can anyone lend me a helping hand with some solid advice that may fix my issue?

                                                                

                                        

Mike458 New Member

Mike458

Posted
Posted

I have a 2017 5.3l Sierra the transmission has had a bad clunk for about a year and half now. Also had a low speed shutter when on the gas poor performance lack of power.  I ended up removing the flapper valve in the exhaust before the muffler and so far instant results. Better power smoother acceleration. And so far no clunking. Next step is to remove the muffler and maybe the resonator and just run a straight pipe.  

  • 3 months later...
InVision Enthusiast

InVision

Posted
  • Author
Posted

Well it is official now after 5 trips to dealer(s) for a stumbling transmission.  GM has cleaned it's hands of "Stumbling Drunk" syndrome.  Says it is normal.  Not sure what Truck to buy now.  Such BS.  I have owned GM trucks for 35 years.

 

See attached notice.  Truck 

 

M

 

 

Scan.jpeg

Scan 1.jpeg

mnm99 Enthusiast

mnm99

Posted
Posted
On 12/3/2019 at 4:05 PM, InVision said:

Well it is official now after 5 trips to dealer(s) for a stumbling transmission.  GM has cleaned it's hands of "Stumbling Drunk" syndrome.  Says it is normal.  Not sure what Truck to buy now.  Such BS.  I have owned GM trucks for 35 years.

 

See attached notice.  Truck 

 

M

 

 

Scan.jpeg

Scan 1.jpeg

Let me get this straight....GM is saying this condition is normal? This document came out on October 8th 2019 right? I would assume by law they have to let you know this before you buy the truck. This is insane.. They didn't let customers know it was normal.

  • 1 month later...
MD11G200 Enthusiast

MD11G200

Posted
Posted

The flush done with the new fluid and it helped tremendously both the shudder my truck eventually developed as well as the horrible clunky downshifting. Hard downshifts not gone but much better.

Through consistently filling out the emails sent to me by GMC to rate the dealer( sent very delineated emails responses to surveys about how pissed off I was after 5 dealership visits and no fix) after work was performed I was contacted by a regional guy from GMC who offered me 3 options to try and help:

1. Have field engineer come out an drive my truck(since flush fixed MOST of the problem elected not to do this)

2. $4500 cash towards the purchase of any new GMC vehicle, I would have to negiote the price with the dealership, then they would apply the $4500 to the deal( don't really trust another new GMC vehicle, so didn't do this)

3. extend my transmission, transfer case and trans axle warranties and all related items another 5 years/75,000 miles from the trucks current milage. ended up with a warranty on those items good til 01/03/2025 or 118,335. Was best option for me since I drive my truck about 15-18K a year.

 

I would say to anyone having transmission problems be sure and always answer dealership surveys if you receive one. Only time will tell if my transmission starts all the bad clunky cramp and shudder again.

 

Hope this helps someone

14LTZ-1LZ Enthusiast

14LTZ-1LZ

Posted
Posted
On 8/16/2019 at 1:29 PM, mrwarrior737 said:

I have a 14 with 6.2 with 6 speed and tow pack.

Terrible trans issues with it stumbling all over it self. Even makes a slack noise when you are on and off the gas... I cant tell if its in the transfer case or transmission.

I have been to the dealer multiple times.

Last 2 times I got charged 120$ inspection fee and they still found nothing.

I have been handed a bulliten 2 times about transmission clunk and slack noise.

 They cant fix the high speed shutter. Claim everything is within specs.

Monday it was to the dealer and 40  miles later on the odometer the tech claims he found nothing, nothing at all. Everything was good to go.

I have 2 friends with the truck almost exact build, motor and trans, Which do not make this noise or have a shutter or stumbling trans at low speeds

I can let off the gas and get back on it and recreate this sound while driving every day.

Like a slack isse somewhere in the system.

 

I attached a video if the sounds. It stumbles through the gears as will.

 

 I have 2 videos on this already and the dealer cannot help.

 My truck is still under warranty for another 5k until I roll 60k. I feel like they are waiting me out to run out of warranty but I explanined ot the prick 3 times I paid for a 84 moth 100 k extended and supplied my documents.

 

I am on my last nerve wit the truck. Can anyone lend me a helping hand with some solid advice that may fix my issue?

                                                                

                                        

Sounds (shuddering) like your TC is going out or is already gone, that's how my 14 LTZ sounded until the transmission went. Just got it replaced under the extend warranty I bought. Have them drop the pan and see if there metal shaving in the pan. If it's still good replace the trans fluid with AMSOIL trans fluid. Good Luck.

gtbigup01 Enthusiast

gtbigup01

Posted
Posted

Welp just logged in to to see any new updates on how the 10-speed was doing. Considering it was a joint venture with Ford. Since  the F-150 owners have the 10-speed in it and they also have a class action lawsuit for the same issues as our 8-speed, its just a matter of time before the 6.2 / w/10-speed starts doing the same thing.

 

For the record I have a 2017 5.3 and have had this problem 2 months after I purchased my truck new. It now has 87K miles on it (yep 2 1/2 yrs), and the problem still exists but i don't worry about it anymore. It drives, and when it dies well lets just say this was my 1st domestic vehicle and it'll be my last. With the clunky shifting (thought i just got rear ended), to the hesitation on acceleration I will say that at least it hasn't left me stranded anywhere anytime during my ownership and I've only had 1 other issue which was corrected by tightening strut bolts. This is the 1st vehicle I've ever put 87K miles on and since I do 106 miles daily just for work, then 2 more years and this truck would have probably done itself in. Who knows.....I've lost confidence in the brand. Glad I'm not a fanboy or i'd make all type of excuses for GM lol.  Sure do like the AT-4 though...but they can't sucker me twice. 

  • 2 months later...
flyingfool Senior Enthusiast

flyingfool

Posted
Posted

buy the toyota fullsize truck ,  only thing i dont like are OHC's on v8.. but they should be reliable

i dont hear these problems from the camaro owners, i would see if the dealer could reflash the tcm with the camaro or corvette software tune

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