gm tsb 18-na-355 transmission flush

[flyingfool]

have you done a trans relearn procedure ?  ask the dealer they have the special tool to clear the memory in the tcu

 

part of the flush procedure , requires the tool to back flush solenoids and all the circuits. , just draining the fluid and reinstalling fresh  stuff wont do jack

Edited August 18, 2020 by flyingfool

[Colossus]

15 hours ago, flyingfool said:

 just draining the fluid and reinstalling fresh  stuff wont do jack

Exactly. 

[cstmg8]

Had the 20 quart service done under warranty today. Drives better already, and I'll report back after 200 miles.
Coughlin Chevrolet in Pataskala, gave me no resistance at all doing the tsb under warranty.

Thanks for the info.

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[DrMikeG2]

On 8/14/2020 at 11:02 AM, reardiff said:

Been curious about this myself. I have a 2017 with similar symptoms, fairly minor compared to what some others have posted about on here but can tell it's there. Been to two different dealers and neither want to do anything about it saying 'normal' along with the occasional clunks and hard down shifts.  My 3 year warranty expires in two weeks so guessing anything under warranty won't happen at this point. 

 

What's the difference between the flush process outlined in the TSB vs a regular transmission flush  the dealer would perform for routine maintenance?  I'm just over 30k miles and thinking it may be good time to just do a flush but this actually solve anything or is there a specials procedure that needs done? 

It's a regular flush/fill but they need to use the more expensive synthetic HP Trans fluid.  We brought ours in 2 days ago and they were going to replace it with the same factory fluid.  Using this fluid (photo) eliminated our shudder.