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

Robert F · March 13, 2020

I'm flustered

Took my 2018 sierra for service twice

Just recently they flushed my transmission.

Shifting from 1st do 2nd is terrible.

Both times they claimed no harsh shifting was found.

I will go there once again but thinking it might be just waist of time.

Agriont · March 14, 2020

Had the same thing done a couple of weeks ago. Seems a little better. Shifting is nowhere near as quiet as when it was new. Keep going back until something is found to remedy it, I plan to.

LDM · March 18, 2020

Had the TSB 18-NA-355 performed on my 2018 yesterday. Mine wasn't having any major shuddering issues but when cold my 1-2 shift was very delayed and harsh. Drove her to work this morning and no 1-2 delay at all with the new fluid. Hopefully this will be a permanent fix as it was really annoying.

Also, no issues from my dealer, they took it right in and did it without any questions or excuses. No arguing about if it needed done or not either, although at this point most dealers are probably well aware of this TSB.

Agriont · March 19, 2020

21 hours ago, LDM said:

Had the TSB 18-NA-355 performed on my 2018 yesterday. Mine wasn't having any major shuddering issues but when cold my 1-2 shift was very delayed and harsh. Drove her to work this morning and no 1-2 delay at all with the new fluid. Hopefully this will be a permanent fix as it was really annoying.

Also, no issues from my dealer, they took it right in and did it without any questions or excuses. No arguing about if it needed done or not either, although at this point most dealers are probably well aware of this TSB.

Same but definitely notice the shift in first and second when cold. It wasn't like this when new.

LDM · March 19, 2020

32 minutes ago, Agriont said:

Same but definitely notice the shift in first and second when cold. It wasn't like this when new.

I didn't buy my 2018 new so I can't say if it did it when it then or not. I didn't notice the 1-2 cold shifting issue until probably 100-150 miles after I bought it. I tried resetting the transmission learn data first, which really didn't help at all but I waiting until I had another 1000 miles on the truck to be on the safe side. Still never improved, so I decided to have the dealer do the TSB.

Bikemobile · March 19, 2020

The shifting on my 2017 is 98% fixed and I’m super happy. Going on 6 months after repair now.

LDM · March 20, 2020

17 hours ago, Bikemobile said:

The shifting on my 2017 is 98% fixed and I’m super happy. Going on 6 months after repair now.

Good to know, hopefully it will be the same on my truck.

Gtaw86 · April 11, 2020

On 4/9/2018 at 2:24 PM, benny12 said:

Was that the 16-NA-412? Or something else?

I only have trouble with the hard shift from 1 to 2, mine is going to the shop in the near future and would like to deal with it in one visit.

Do you still have the hard shift? Mine is doing it also and now at the dealership. What did they do to fix it?

Bikemobile · April 11, 2020

5 hours ago, Gtaw86 said:

Do you still have the hard shift? Mine is doing it also and now at the dealership. What did they do to fix it?

Have you tried the new fluid yet?

Agriont · April 11, 2020

5 hours ago, Gtaw86 said:

Do you still have the hard shift? Mine is doing it also and now at the dealership. What did they do to fix it?

Had the transmission flush and fluid changed. Still not as liquid smooth as it was new but haven't had the kick so often between 1-2 and back. If it gets worse, I'll bring it back.

Bikemobile · April 12, 2020

Mine is still not 68 Impala 3 speed perfect but its pretty good. The new fluid helps alot. I still think the remaining issues are programming related.

I’ll be trading mine in the day before my extended warranty expires though. That transmission looks expensive to replace. Im not convinced this new fluid isnt just a band aid that will shorten its life through additional slippage and heat. We’ll see if/when i get to take my camper anywhere this summer.

mookdoc6 · April 12, 2020

3 hours ago, Bikemobile said:

Mine is still not 68 Impala 3 speed perfect but its pretty good. The new fluid helps alot. I still think the remaining issues are programming related.

I’ll be trading mine in the day before my extended warranty expires though. That transmission looks expensive to replace. Im not convinced this new fluid isnt just a band aid that will shorten its life through additional slippage and heat. We’ll see if/when i get to take my camper anywhere this summer.

The slippage is removed from these 8speeds...hence the feeling of the shift. The transmission is expensive to replace luckily they are super ROBUST! The outright failure rate is non-existent compared with 6speeds!

The 1-2 on cold starts and DECELS will never go away it's done to prolong the life of transmission. The quicker you learn to put more meat into the peddle and stop trying to have a Drive by Wire transmission to compensate for that lethargic peddle input it will constantly stumble as it's not designed for driving at 1100 rpms and shifting ohhhhhh so casually. Try it and report back in couple months?

Bikemobile · April 12, 2020

Yes I love how this transmission drives at 3/4 or full throttle. It is the off the gas, on the gas turning in parking lots that it falls all over itself.

ThundahBeagle · June 15, 2020

As someone else already asked, is anyone else also experiencing this with the six-speed transmission? I have a 2014 GCM Sierra SLE, 6 speed and I feel this. I've had passengers look over at me exchanging sideways glances wondering what the hell just happened

jjdurrant · January 20, 2021

Wow.. I am not alone. Ha! I bought a 2017 Yukon Denali with 63k over the weekend. It was a CPO. No clunks but it shifts hard at times and lots of shudder. Dealer seems great and they are changing the fluid tomorrow. Will report back!

Edited January 20, 2021 by jjdurrant