Makitso

Electronically controlled transmissions typically have a limp home mode that is controlled mechanically
by the shifter and usually will provide these basic functions in the event of a total TCM failure: park, neutral,
reverses and one forward gear like forth. Try disconnecting the electronics from the trans and see what it will do.

subieworx

I don't have the shudder as I have AFM valves disabled in my tune, but I have had a few issues with my trans.

Originally had a problem with it slamming into gear when going from P to D/R on a cold start. I was also getting a very hard downshift from 8 to 7 and 7 to 6 on the highway under light acceleration.

Took it in to dealer and they replaced the stator and added a check valve that was supposed to help. It lessened the issue, but was still present.

After this was done I found that an axle seal was leaking and had to take it back in.

Got the car back in a day and within a week found the axle seal was still leaking, but only after putting the car in the air to reattach my cat back that had fallen off.

Took it back to dealer for the jerky cold start and for the leak and hard shifting. They called and said they were replacing the entire transmission this time.

Should have it back next week and hopefully it will finally be good.

Car was purchased with 29000 miles and now has 32000 and is a 15 z51.

wbrands

I have followed all the A8 discussion here since buying my car new in December 2015. From day one, I have been concerned about the rpm fluctuation in V4 that started out as 100-200 rpm at highway cruise speeds. My first early on complaint to the dealer resulted in a TCM reflash that reduced the fluctuation to around 50 rpm. Around the two year point and 17,400 miles, I first experienced the "rumble strip" feel and brought this to the dealership's attention when having other service performed. They did another TCM reflash/update and replaced the idler pulley (leaking oil) and said that could have been the cause of the shudder. I have a Range AFM eliminator that I usually use, so I didn't experience the problem much if at all for quite a while.

However, on a recent road trip, the shudder was really bad, so bad my passenger (who knows nothing about cars) asked "what's wrong with your wheel?". I made an appointment with my local dealer as soon as I got home. This time, I finally convinced my technician I have a TC issue. 2016 Stingray with a build date of 9/15 and 24,292 miles on it. They did the flush and fill according to the current TSB yesterday.

On the 25 mile trip home (mostly highway) the shudder was not noticeable and the rpm fluctuation may have been slightly less. I don't know if it is the placebo effect, but it even seemed like the transmission shifted smoother on the trip, especially the 1-2 and 2-3 shifts. However, on a short local trip later in the day, I think I may have felt a very slight shudder, so the jury is still out. I guess I have another 150 miles or so before I will know if the magic new ATF will cure my problem.

It seems funny to me that anyone complaining about TC issues on the forum always gets loads of responses to get a Range device. I have one, use it most of the time, and like the way the car drives and performs with it. However, I want my car to perform with all the technology the engineers at GM designed and decided to put into it operating correctly. I don't want to have to defeat the technology to get the car to perform acceptably. I am not so destitute I have to have the extra MPG or two that Eco Mode gets, but it is sure nice to brag about a 460 hp sports car that can get better than half the mileage of a Prius and be loads more fun to drive.

I mention this last point because I have another thread on here asking a couple questions and most responses so far say "get a Range", My questions for those of you that have been down this road before are:

1. How long after the flush and fill did it take for the shudder to reappear?

2. Does the car need to be re-aligned after the rear end comes out for a TC replacement?

subieworx

The car doesn't technically need to be realigned, but it probably should be.

wbrands

Thanks, subleworx. That is kind of what I was thinking. I am sure there are some sort of locating pins to get things more or less back where they belong but it is probably cheap insurance considering the price of tires.

C7 Sandy

mikez06

Hit 15,000 miles on my 2015 Z51 2LT and now have the dreaded shudder. I will be calling my service advisor to get the triple flush, hope that helps it. Guess it's my turn now?

macjac69

I had the dreaded shudder issue at 25,700 miles on my 15 Stingray Z51. Stealership did the triple flush and it seemed to help. Still seems as though i have a very minimal. studder of sorts.This is my first corvette and it occurred about 500 miles after I purchased it back in late June sigh. So I may just be feeling something not to be worried about.
Also had a right rear CV axle replaced at the same time under warranty and two weeks after it crapped all the grease out of itself (outer boot I think) so I had to take it right back in.
This is my second GM product. I bought a 09 Southern Comfort Avalanche trying to do my best to support the tanked economy back then, and it had a leak in the transformable back window/tailate that never could be fixed wound up selling it.

Tx_94vette

Pfrobin

MidLife+

My 2016 Z06 A8 experience so far:
I noticed the shudder about a month or so ago and took it in to the local service department.
1st - flushed fluid and replaced filter
2nd - 300 miles later shudder was still present so they replaced the torque converter.
3rd - 500 miles later some shudder is still noticeable and experiencing rough/delayed shifting between 1st and 2nd. They ordered me a new valve body today (4 to 6 weeks out).

If this fixes ALL my transmission problems I'll happier than a pig in $hit.

Rick

Pfrobin

BlackHoleGravity

I still don't understand why some people have problems and others don't...and also why those that have problems cannot get their cars fixed properly most of the time??? Auto transmissions have been around for a long time, this shouldn't be rocket science...

Pfrobin

blue max

I am a sort of tech rep for our club of over 100 plus with around 34 c-7's. We have had seven TC failures. Mine a 16 Z-51 is not one of them yet. Yesterday we took a drive from the Knoxville area to north Atlanta. I was watching the tach and it was going up and down over 500 rpm. Cruise on level highway around 70mph. I put the shifter in manual and it stopped immediately.
On return I am watching the tach and it was solid as a rock. no movement go figure. I don't have the hard first shift. Its a little slow starting to move in reverse.
Some of our members did not attend our little session at my house going over some of these issues where not even aware of what the TC problem was until late into the problems.
Good news we have two dealers in the area who seem to know how to take care of the problem. Owners said the cars drive better than they did brand new. Some have been required to do the triple flush but still had to get the TC done. We are not seeing the triple flush as productive and may just postpone the problem
So we have 7 with the torque converter replaced. Not so good on the high percentage of TC's replaced.
I almost forgot I have 14,000 miles on the car

767guy

The short answer to your questions are,IMHO ,
1) It is an engineering/design problem and without a redesign band aid fixes usually don't work. My understanding is that to make the C7 A8 transmission fit it is like a '"squashed" C6. That combined with the harsh running engine in V4 mode and the slippage designed into to TC to mitigate the roughness you have a recipe for failure.
2) Many dealers still do not even know about the issue or pretend they don't and tell customers it's normal.Communication between GM engineering and the dealerships is extremely poor.....not in all cases but in far too many as reported by forum members experiences.

C7 Sandy

Thunder22

Sorry if this was covered already, but I couldn't find the answer:

Is the TC replacement and flush covered under the 3 year B2B warranty or the 5 year power train? Obviously it would be better if it's the 5 year power train.

MidLife+

I would think if your three year B2B is over it should be covered by the five year powertrain warranty. Not 100% sure cause I have both available.

Kenafin

Powetrain. Had the flush done at 49,000 miles. She's showing signs of problems again (now at 53,000 miles) so she'll be going back in again.

-Kristen