TSB 18-NA-355 performed yesterday

[BloodVessel]

2015 High Country 6.2.  Had torque converter replaced about a year ago to correct tcc shudder.  Started again a few days ago and took back to dealer.  They performed bulletin 18-NA-355 (flush transmission w/ Mobil 1 ATF and said to drive for 200 miles for full effect.

Just wondering if anyone has had success with this procedure to correct tcc shudder and hard shifting.

 

Thanks!

[m3n00b]

Was your shutter at 55-75mph off and on where the rpms raise a little and the steering wheel shook in your hands?  

[BloodVessel]

Very close!  Actually mine started at 45mph and up.

[B R A D]

My '16 was flushed with some sort of new and improved fluid. Drove great for about 1000 miles then It came back.

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[Sierra Jon]

Not really what I was hoping to hear. Mine is going in on Monday.

Anyone else with an update on this TSB?

Thanks,
Jon

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[Copboy4090]

Mine is going in Saturday. Felt like driving over a wash board. 

[Sierra Jon]

They replaced my torque converter under warranty. Doesn't exactly give me a warm and fuzzy but they took care of it.

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[M1ck3y]

I was under the impression gm stopped all tsb's for 8spd/tcc. The class action lawsuit for the 8l90 got thrown out because gm stated that their warranty covers manufacturing defects not poor design. After that, all work on 8spds was cut immediately and they stopped trying to fix it. I dont have the link for that specific tsb but do a quick search on google and you'll find it.

[Sierra Jon]

I was under the impression gm stopped all tsb's for 8spd/tcc. The class action lawsuit for the 8l90 got thrown out because gm stated that their warranty covers manufacturing defects not poor design. After that, all work on 8spds was cut immediately and they stopped trying to fix it. I dont have the link for that specific tsb but do a quick search on google and you'll find it.

Pissa. More great news. Thanks for the info.

My TC was replaced because my truck is CPO. Let's hope if it happens again it's before 100k...

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[M1ck3y]

https://gmauthority.com/blog/2020/04/general-motors-looks-to-have-lawsuit-over-eight-speed-transmission-defects-dismissed/#:~:text=General Motors is looking to,8L90 eight-speed automatic transmissions.&text=GM has sent technical service,defects since at least 2015.

[Chris Giff]

On 7/12/2020 at 8:28 PM, Sierra Jon said:

Pissa. More great news. Thanks for the info.

My TC was replaced because my truck is CPO. Let's hope if it happens again it's before 100k...

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Just had mine flushed today in accordance with TSB 18-NA-355.  My 2017 Silverado High Country is also a CPO.  Should I have asked for a torque converter replacement?  It seems to be driving great now after the tranny fluid flush and fill.  Thanks.

 

Chris

[Sierra Jon]

Just had mine flushed today in accordance with TSB 18-NA-355.  My 2017 Silverado High Country is also a CPO.  Should I have asked for a torque converter replacement?  It seems to be driving great now after the tranny fluid flush and fill.  Thanks.
 
Chris

It may be ok but down the road the TC will likely need to be replaced... based on what I've read from other people's experience anyway. How many miles do you have on the truck?

[midwestdenaliguy]

My dealership did 3 things all at once to fix the shutter for me: triple clean flush with new tran fluid, replaced TC, and reprogrammed the tran with an update from GM. This was done last year and while it was technically outside my warranty (miles) they got GM to cover the entire bill. I've driven ~35k miles since this was all done and have not had the shutter return. Sorry, cant say if it was any one of those in particular that fixed it. The dealership said they didn't want me coming back after only doing one of those so they did all 3 at once.

[Chris Giff]

On 8/19/2020 at 6:15 PM, Sierra Jon said:

On 8/19/2020 at 4:10 PM, Chris Giff said:

Just had mine flushed today in accordance with TSB 18-NA-355.  My 2017 Silverado High Country is also a CPO.  Should I have asked for a torque converter replacement?  It seems to be driving great now after the tranny fluid flush and fill.  Thanks.
 
Chris

It may be ok but down the road the TC will likely need to be replaced... based on what I've read from other people's experience anyway. How many miles do you have on the truck?

I agree.  I have read the same remarks.  It's a CPO, so I am hoping if it does need to be replaced it will still be covered under warranty.  It currently has 38k miles.  Thanks for the reply.