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Abonino

Infamous 8 Speed Transmission Clunk - Dealer/GM Current Position on the Issue?

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Had mine flushed this morning. It was covered under warranty even though I don’t have the “shudder”.

Have only driven 100 miles, but seems to shift a bit smoother... time will tell.


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I had the flush done a few days ago. 200 miles and the shudder is gone. However, the truck still shifts like it is confused. The clunk is still preset. Taking it in Thursday for a TSB covering the valve body. I will report back after the fix is done.

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This is the main reason I traded in my '15 - I complained about the transmission every time I took it in for anything, and was basically told that everyone has the same complaint and there was not a fix. They flushed the fluid 2 or 3 times, replaced the TC and it was still a piece of shit. I had the extended warranty, but that had a $250 deductible every time I wanted to use it, so I traded it in on a '18 Denali - so far (3200 miles) the transmission is night and day different... although this one has the same 70mph shake as the '15 did. 

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What was up with the transmission in your 2015? My 2018 doesn’t have any shaking at higher speeds, just the low speed clunk upon throttle application 

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Yeah, when I ordered my 18, CC, 6.2 the owner (a close buddy of mine) of the dealership looked at me and said you know, you may have issues with the transmission clunking, told him I’ll bring it back to him and he’ll fix it, he laughed. First week, drove to Austin and noticed it, then while parked in a parking lot it felt like I got bumped, no one around but the transmission just thumped hard. I later did a tune, turned off the AFM and along with not having shifting issues, haven’t felt the thump since

 

 

Sent from above

 

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1 hour ago, TXGREEK said:

Yeah, when I ordered my 18, CC, 6.2 the owner (a close buddy of mine) of the dealership looked at me and said you know, you may have issues with the transmission clunking, told him I’ll bring it back to him and he’ll fix it, he laughed. First week, drove to Austin and noticed it, then while parked in a parking lot it felt like I got bumped, no one around but the transmission just thumped hard. I later did a tune, turned off the AFM and along with not having shifting issues, haven’t felt the thump since

 

 

Sent from above

 

You did the tune in your 18? What tune did you do? I want to do a black bear tune but it just sucks that they can’t tune the TCM. It’s always seemed to me like this whole deal is simply a tuning issue on GMs part

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You did the tune in your 18? What tune did you do? I want to do a black bear tune but it just sucks that they can’t tune the TCM. It’s always seemed to me like this whole deal is simply a tuning issue on GMs part


Mine is just a SuperChips tune, set on performance along with disabling AFM and other preferences. Did notice acceleration difference too on my 6.2 after my CST lift and 34” Nitto Ridge Grapplers


Sent from above

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For anyone watching this thread,  I'm  scheduled to go in this Monday 3/18.  My truck would get the shudder literally nearly everyday for the weeks leading up to this. 

 

I kid you not, since I scheduled this a few days ago, it has only shuddered one time and has overall been shifting better than usual.  Like wtf???

 

The way my service advisor talked it sounds like they will perform this flush no matter what the results of the test drive are. 

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Does anyone know if there doing this same flush on the 6 speeds?

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3 hours ago, SkiDooNick700 said:

For anyone watching this thread,  I'm  scheduled to go in this Monday 3/18.  My truck would get the shudder literally nearly everyday for the weeks leading up to this. 

 

I kid you not, since I scheduled this a few days ago, it has only shuddered one time and has overall been shifting better than usual.  Like wtf???

 

The way my service advisor talked it sounds like they will perform this flush no matter what the results of the test drive are. 

Let’s hope they aren’t just making you feel good...I’m told that the PICO test needs to show something for GM to pay the dealership for the fluid and time. Maybe you have a good dealer  :thumbs:

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I was just at the dealership to get the flush done.I told them I had the shudder which I don't just hopping to get the flush done.They said just like SS502 said it didn't hit the PICO test.There not allowed to change the fluid unless it hits the score needed.

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Ill be so frstruated if thats the case.  I will have to work with my serivce advisor for next steps... come back in a couple 100 miles etc...? Blahhh i dont even want to think about it!! 

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Dropped it off Monday night. Didnt hear back today.  Maybe they were like "oh man this trans is f'ed we gotta put a new one in"

 

LoL wishful thinking!! 

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On 3/12/2019 at 10:21 PM, dewey05sd said:

I had the flush done a few days ago. 200 miles and the shudder is gone. However, the truck still shifts like it is confused. The clunk is still preset. Taking it in Thursday for a TSB covering the valve body. I will report back after the fix is done.

 

Can you share info on the Valve body TSB?  Just got off the phone with my Service Adviser.  He updated me that the trans tech is on the phone with GM Tech Support trying to upload whatever data files they created to prove that there is an issue with my trans.  He also mentioned that they may need to replace the Valve Body. 

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I wish I had more information. I ended up taking it in and I had the shop foreman ride with me. I wasn’t able to replicate the confused shifting. Not that it helps me, you or anyone for that fact but he did say out of 300 transmissions he has serviced for this problem only 2 he said shifted flawlessly. At this point, I am just going to drive it until something serious happens and hope GM comes out with a fix for it.

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