[SuperSound]

Originally Posted by 1LE Red Dragon

From what I heard from my Chevy dealers shop foreman. Who is an EFILive tuner. He says that GM has had the slip percentages in the auto transmissions for sometime before the A8 trans came out. There was no issue with those. So the trans slip percentages to soften up the response can work properly long term without issue. The mechanical issues with this transmission/TC seem to happen with the slip percentages in them. The friction modifiers are supposed to help with the shudder issue, but evidently there are some mechanical differences with SOME of the TC in the A8 transmissions. They tried to change fluids based on findings of failures. The TC can be damaged if it goes long enough with shudder.

So my guess is they tightened up on the tolerances on the TC manufacturing, and changed the fluid as a double fix going forward in 2018. I dont think they changed any slip percentages in the TC tuning. After all, going from past years, the slip percentages have never been a problem, so it is possible to have a shudder free transmission long term with TC slip programmed in.

My guess is the TSB was meant to cover all years up to an including MY18. Just in case there happen to be some leftover issues, that they did not expect. Its an all encompassing TSB for the A8 trans.

FYI, my 2016 A8 had the shudder begin at 8k miles. I took it into the dealer. They did the triple flush properly, and put new fluid in, and it ran better than ever until the day i traded it. It appears that 80 to 90% of the time, if caught early enough, the triple flush and new fluid fix the problem. The other 10% could be actually TC damage, wrong fluid, or technicians not following the procedure precisely. From an Engineers perspective, the answer AL gives seems straight forward, and honest enough with what they actually know. Believe it or not anomalies do happen from time to time, that logic and engineering troubleshooting cant explain. My $.02

Exactly. Some people think that just because they turn off something in a tune that's the cause. A quick Google search turns up shuddering issues for the previous A6 trans too, just in nowhere near the numbers that the A8 has shown since it's launch.

If the fluid is not up to spec and the TC starts to wear slowly, it doesn't matter if you tuned out the slip values, something is going to break. It's only a factor of time.

Speculation over whether GM QC has really sorted this out is another story.