I was seeing a 200rpm swing before the flush.
not sure about the miles after the flush but at least 1500.
The shutter was gone after the flush, The shifts greatly improved.
I always thought the shifts were lazy at mild throttle.
They are much better now.
They were always great at full throttle.

All I can do now is keep an eye on it.

 

Did the flush also eliminate the RPM variations in AFM (V4) mode with the cruise control set to about 70 MPH?

I see about 100-150 RPM variation without any shutter.

John

 

Glad to hear that is working out for you. It just blows me away that just changing the fluid can fix something like that!

 

This is my first report on this thread as my first T/C issue occurred in March 16' at around 7,500 miles. T/C was replaced in early April 16' at 8K mi. I also broke a drivers side CV joint in Feb 16' but doubt this was related. My 15' Z51 A8 was built the last week of Jan 15'.

A month ago it was in to replace the 2 piece rotors as I had a vibration under braking. Last week, the first time I had gotten it to highway speeds, I noticed the RPM variation and shudder - driving in high 70's in 8th gear - Eco mode (16,500 mi). Dealer immediately agreed and flushed the tranny and replaced filter. Dealer says they will replace T/C again or other options if issues return. Only driven home -5 mi, but so far I couldn't duplicate rpm flux or shudder. Biggest improvement is the shifting and minimal vibration when stopped at traffic lights. Before taking it in this time, I thought it was shifting haphazardly and jerky, but also wondered if I was just feeling things due to the overall issue. Obviously I wasn't.

Rotor issue is worrisome as they only replaced the fronts going to 1 piece from the troublesome 2 piece. Also had a radio issue that took over 2 weeks to finally get the correct installation clips as there were part# issues. Not sure if it was bad info on repair diagram, parts mis-labeled or what, but nothing that simple as a connector should take over 2 weeks to receive.

Also.. from what I have read and verified with my servicing dealer (Hendrick - Naples), our A8's will go into V-4 operation in all modes ECO -TRACK, if the shifter is in "D". You can keep it in V-8 mode by shifting into "M" but you have to do all the up-shifting.
As for DOD/AFM, there have been failure issues since it first was added to GM V-8's. My son had his fail in his 09' G8 GT 6.0L. Since he had a second tuned ECM it never ran in V-4 mode after the first 1,000 mi. This happened 1 week before his 5 yr drive-train warranty expired. With the original ECM back in, it got fixed free. They told him a DOD lifter had failed so all were replaced. So.. going to a Range plug-in for your OBDII port isn't a guaranteed drivetrain solution.

I love this car, but have had more major issues with it than I have had in total in the last 10 GM vehicles over the last 20 years. And.. the half dozen Ford products I've owned in that time have had no major warranty issues period.

 

Had a nice talk with Rich from Able Chevy. He has seen this before and thought it was basically a glitch that happens from time to time. I cleared the codes, per direction, and the code has not returned. Trans is shifting perfect. Hopefully it stays this way! My wife commutes 50 miles a day. Two days in and no problems.

 

Glad to hear that worked out for you.

 

lucky you, mine is in the transmission dept. getting diagnose.

 

Is there any mention if the A8 torque converter issue has been resolved for the 2018 model? Curious if GM has been proactive in getting this somewhat common issue resolved.

 

Good question. They are on the third iteration of the TC. I believe that and the new fluid that is installed at the factory is their best fix so far.

 

i have a 16Z auto, what should i do to prevent problems? Anything?

Or should i just wait for it to fail and take it to the dealer? I don't track, but i drive pretty hard and fast.

What happens when it fails? Is car down for the count? or is it still drivable?

 

 

1) No prevention requited, IMHO , just drive it. For the money I paid for mine I am not inclined to baby it or avoid V4 mode because it may "grenade". Some are installing a device that prevents V4 mode but I have not seen any engineering or scientific reports that proves keeping it out of V4 mode will prevent a failure.

2) If TC fails take it in to the dealership for diagnosis and repairs

3)If TC fails, driveable......not aware of any one on this forum reporting a roadside breakdown as a result of a defective TC.

4) The last iteration of the TC being used is a part # ending in ...631. I think the change over to this was about November 2016 , if memory serves, so if your car was built after this the chances of a failure are very slim is my understanding...........

 

Thanks for the help.

So if the TC does fail, they will upgrade me to the 631 variation under warranty I assume?

 

You have a 2016 A8. If you experience shuddering, the first step would be to flush the fluid and to fill with the new mobil LV ATF fluid.
On early 2015 A8s , the repair involves replacing the TC first.

 

The only way to prevent the problems is to trade the car in. However, even though I had just about ever transmission and TC issue, none of those ever caused the car to stop and leave me stranded. A couple of other things did, but not those issues.

 

what causes it to fail? heat? or high torque situations like drag strip digs etc? Or lots of shifting, people playing with the manual mode paddles etc?

I would rather mine fail while it is under warranty, before i mod it, if i decide to.

 

No, there is nothing you can do like paddle shifting that causes the TC to fail.I had three transmission tear outs on my 2015 at three different dealerships.Each time I asked what the cause of the defect was and the response was that the information was not provided by GM......and that is not surprising as auto manufacturers are not in the habit of explaining to the public the nature of design defects or parts supplier defects.
Some of our forum members have technical expertise regarding transmissions and the general consensus seems to be ..." In V8 mode the engine runs smoothly however in V4 mode the engine is not as smooth. To dampen the rougher running engine the TCC apply ( torque converter clutch lockup) rapidly cycles between lock up and released to absorb the V4 operating roughness. In the earlier versions of the TC this caused wear/failure that resulted in the reported symptoms like driving on rumble strips".
According to forum members reports those that had their TC's replaced after about Jan 2016 with part # 24280631 and the new transmission fluid that became available about the same time have not reported any subsequent failures. The exception was one forum member who reported he had a TC replacement , part off was 24280631 and part on was 24280631, however there were few details regarding the nature of his problems and it very well may have been an incorrect diagnosis by the repair shop.
Also many forum members are also reporting short term success with the flush procedure.Other GM vehicles with a version of our A8 have the same problem. On those forum boards folks are reporting that the flush , at least in the short term, has solved their problem.
I now have a 2018 ( non Z51 ) A8 built in June 2017 with just over 5000 miles on it and it has non of the TC issues my previous car had.

 

This is obviously due to bad design and substandard materials used for the cheaper corvettes. GM will not admit or own up to it. They will simply replace it under warranty and you are up the creek without a paddle after that.

 

Do they only replace it once?

 

I expect you are correct with respect to design and materials/workmanship from some suppliers.

For those of us on this thread have you seen one of the questions for Tadge week ending Feb 12th you can vote for ?????????

It relates to the four versions of the Torque Converter we have seen on the C7 .

The voting thread is just above all the "stickey " threads on our forums
C7 General Discussion page.