My 2016 Z06 A8 is fine but it has either been in manual mode or had a Range module installed since the moment I took delivery at the museum. The root cause of the major A8 issue is GM's ridiculous implementation of V4 mode where the torque converter lockup clutch is continuously modulated during V4 mode to attenuate the amount of engine vibration transferred through the rest of the powertrain. Lockup clutches (realistically no friction clutch) is going to stand up long term to this type of abuse where it is being engaged and disengaged multiple times per second. "Magic" fluid with friction modifiers can help reduce and to some extent mask the effects of wear from this operation but anyone who wants to keep their car long-term needs to seriously consider if they want to subject the transmission to this increased wear. GM MAY have addressed the increased oil consumption issues with their prior implementation of AFM but I don't plan to empirically test that premise either.

The only quirk I have with my A8 is in order to avoid an initial harsh 1 to 2 shift, while the car is still stationary after the first start of the day I shift to second and then back to first. The clutch pack associated with this range has a large fluid reservoir that is a little slow to initially fill after sitting overnight and this provides a good workaround to the initial harsh shift. GM may have updated the software to do a partial pre-fill of this clutch pack actuator so this step may not be needed with current production. The pre-fill strategy has been used on many other clutch to clutch architecture transmissions over the years and I have no idea why GM didn't do it in this case since it is under software control.

There is one relationship between the harsh initial shift and shudder. These clutch to clutch automatics depend upon very precise timing of the engaging and releasing clutch packs during shifts and this is accomplished via the controller working with precise sensors that measure input, output, and intermediate shaft speed. When unexpected slippage occurs (indicated via the RPM measurement of the various shafts) the transmission controller immediately responds by increasing apply pressure on the offending clutch pack(s). The initial 1 to 2 harshness occurs because of the slow fill resulting in an initial slip causing a command for an abrupt increase in apply pressure with resulting harsh engagement. Shudder occurs when there is unexpected slippage in the converter because the controller has ordered engagement of the lockup clutch. With shudder you have commanded engagement of the lockup clutch but because of wear there is slippage, when this happens apply pressure is abruptly increased resulting in harsh engagement. Under AFM in V4 mode this converter clutch slippage followed by abrupt lockup is happening continuously resulting in the shudder behavior. If the converter clutch were left completely unlocked during V4 mode operation then there would be no shudder but the already meager mileage gains from operating in 4 cylinder mode would be lost.

You will see the results of this increased wear before you begin to feel it as RPM variation at steady cruising speed will increase until it reaches the point where the controller is actively trying to combat this undesired slippage. By the time this occurs you already have experienced significant wear to the lockup clutch in the converter.

Shudder is very uncommon in the Z06 because it goes into V4 mode far less due to the different operating characteristics of its lower compression, forced induction motor. I suspect GM also made V4 mode engagement less aggressive with the Z06 because it doesn't have the vibration absorbing steel torque tube assembly or the AFM sound control valves which would have a very short life given the additional exhaust heat from the supercharged engine. In any case my Z06 will not be spending any time in V4 mode.

One other caution is that shudder can also come from engine problems and because the shudder problem is so common with an 8L90 (aka A8) transmission that engine operational/power delivery problems are going to be misdiagnosed because techs have become so used to the frequency of the issue with the 8L90 (and its 8L45 lower torque sibling).