[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.

[g26er]

FWIW I have the problem on my 2018 SS w/ A8. Build date is 08/17. Happened within the first 1,000 miles. Dealership did the flush and threw in a couple extras like crushing those areas behind the front wheels where you are NOT supposed to lift the car from. As those areas collapsed, it let the rockers hit the lift arms and luckily it only messed up the bottom of the rockers that can't be seen unless you’re under the car. I have 1,500ish miles and the shudder is still there. The flush never completely fixed it, I'd say 90% improvement at first. The problem is always there but, is worse when the trans fluid is up to temp. Another thing that will get it going easily is when I'm at 25~50mph and it upshifts sort of at the same time I press the accelerator pedal a little to increase my speed.... kind of like it's shifting right into the shudder.

I'm probably going to get a CircleD or Yank converter and have a well-known local shop install it. The way I look at it is what good is a warranty if your car comes back in worse shape than before it went in for service. I love the car but, the shudder is driving me

[MJinNC]

Just got my car back, had the flush and TC replaced prior.. they started this time with the flush again. They were told on Monday to again replace the TC because they had problems with them. Got a call on Tuesday saying GM told them to not replace the TC but to reprogram the TCM. So picked the car up and it rides better than new. I have never watched the V4 to V6 changes before this, but looking at it now it stays in V6 99% of the time. The rpm's are not jumping all over the place and it is enjoyable to drive. I think the TC is the symptoms of whatever is causing the problem. Its either the fluid or programing.

[Evil-Bee-NH]

Originally Posted by MJinNC

Just got my car back, had the flush and TC replaced prior.. they started this time with the flush again. They were told on Monday to again replace the TC because they had problems with them. Got a call on Tuesday saying GM told them to not replace the TC but to reprogram the TCM. So picked the car up and it rides better than new. I have never watched the V4 to V6 changes before this, but looking at it now it stays in V6 99% of the time. The rpm's are not jumping all over the place and it is enjoyable to drive. I think the TC is the symptoms of whatever is causing the problem. Its either the fluid or programing.

Did you ask them what they changed in the TCM. You might want to I'm curious myself to see what they did.

[HackSaw]

YES thats the first time Ive seen a dealer flash to the TCM mentioned

[Evil-Bee-NH]

Originally Posted by HackSaw

YES thats the first time Ive seen a dealer flash to the TCM mentioned

Get ready for "crickets" lol

[SuperSound]

Just for reference, my RPMs never fluctuated at any point while I experienced the shudder. Sounds like the V6 above had something else wrong with it, hence the less aggressive switching to V4 after the reflash. I've heard the same issue reference by other V6 owners but not any of the LT1s.

[mekirk2]

Originally Posted by HackSaw

YES thats the first time Ive seen a dealer flash to the TCM mentioned

I just had mine done - single flush. I stopped in toward the end of the day to see if it was done. At the time, the service adviser told me that they were wrapping up and reprogramming the transmission. I didnt think anything of it until this comment.

Just checked my service paperwork - there is no mention of a reprogram. I might have to check with the dealer again on it.....

[cooper1965]

Originally Posted by mekirk2

I just had mine done - single flush. I stopped in toward the end of the day to see if it was done. At the time, the service adviser told me that they were wrapping up and reprogramming the transmission. I didnt think anything of it until this comment.

Just checked my service paperwork - there is no mention of a reprogram. I might have to check with the dealer again on it.....

You won't see anything on the paperwork about the reprogram (if it actually gets done). No part number, or additional job line is needed. There is only an internal labor code, that we bill GM directly for.

[Evil-Bee-NH]

Originally Posted by cooper1965

You won't see anything on the paperwork about the reprogram (if it actually gets done). No part number, or additional job line is needed. There is only an internal labor code, that we bill GM directly for.

I would think if a customer requested the information they'd have to tell them what was done. Sure it falls under some modification law where work was done but not explained and could cause all sorts of warranty issues for them if someone was bored and decided to pursue it.

[g26er]

Originally Posted by mekirk2

I just had mine done - single flush. I stopped in toward the end of the day to see if it was done. At the time, the service adviser told me that they were wrapping up and reprogramming the transmission. I didnt think anything of it until this comment.

Just checked my service paperwork - there is no mention of a reprogram. I might have to check with the dealer again on it.....

Maybe that's what he said but, really meant finishing up the TCM quick learn or something similar. He could be using the phrase 'reprogramming the transmission' loosely since he probably deals with a lot of people who aren't very 'car savvy' and would only be confused if he started getting too technical. Hope that made sense.

[mekirk2]

Originally Posted by g26er

Maybe that's what he said but, really meant finishing up the TCM quick learn or something similar. He could be using the phrase 'reprogramming the transmission' loosely since he probably deals with a lot of people who aren't very 'car savvy' and would only be confused if he started getting too technical. Hope that made sense.

Went by the dealer today. Asked them if they did anything other than change the fluid. They stated that they had to 'update the TCM'.

[MJinNC]

200 miles now and still good. I will call the dealer when I get close to 500 miles to give them an update and ask specifically what was done when he said he flashed the TCM. They definitely changed something because after the flush and again after the TC swap the tranny hasn't been this responsive to switching out of V4 into V6, which is where most of the shudder occurred. So if it is programming related, I cant figure out why no shudder occurred after the flush and then after the TC change and come back in a short time.

[RockerC]

GM will replace entire transmission. unfortunately, that may take a while as Service Manager informed me they are on allocation and will call to schedule appt when they get one.

FYI: I had the triple flush done and then the TC replacement. Service manager and shop foreman agree the problem is real and affects many vehicles. They went to bat for me with GM. I assume the new trans will also come with software updates that will need to be programmed in. Will update again when trans arrives.