I have a question about the A6 transmission in my 2014 Z51 convertible.
Short history
Purchased march 2024, discovered failed torque tube right away.
Rebuilt torque tube July 2024,service the transmission, fluid and filter, while driveline was out of the car.

I used redline 30704 full synthetic D6 fluid for the transmission, and OEM transmission filter.

I noticed my car likes to run at 1100 rpm when trying to maintain speed.

as an example, if i am trying to maintain 60 MPH, on a flat road, the car shifts up to 6th gear, and requires almost no throttle input to maintain. In this condition, the transmission will studder. If i give it throttle input, it downshifts, and no studder. if i increase my speed to 75 mph, the car runs at 1450 RPM, and no studder, it only studders at 1100 rpm, while trying to maintain speed.
Never shudders under load or while accelerating, only when trying to maintain speed.
My conclusion is the car continues to shift to the next higher gear until that gear holds 1100 RPM, and there it studders. in 25 mph zone, it will shift all the way up to 5th gear, and then studders.
If i run in in paddle shift manual mode, the is does not repeat, i.e. no studder under the same condition.

I changed the transmission fluid from redline back to OEM. ACDelco GM Original Equipment 10-9244 Dexron VI Full Synthetic Automatic Transmission Fluid
Note, no debris in the fluid on either fluid change.
Same performance with OEM fluid as the redline fluid.

I do not know if it had the issue before the torque tube rebuild and initial transmission service, as the backlash in the torque tube was worse then this studder and would have hide it.

So my question is if i need to do another fluid change? or if my transmission is start to fail. Only 68 K miles on it.

I found somewhere a TSB about triple flush, and different fluid as part of the flush, but cant seem to find it now, and am questioning if the OEM fluid i put in it is the one the TSB says to use.

If you any one has the link to the TSB it would be greatly appreciated.

Thank you in advance for your opinions.

 

The A6 in your 14 does not suffer from the A8 Shudder issue, that Tripple Flush TSB and fluid is for 2015 and up A8 Transmissons only

When installing the torques tube you did do the torque tube end play process correct, if not STOP driving the car now as not doing this process will destroy the engine thrust bearing in less than 200 miles ....

if you did then .....
When you say " Studder" describe a little bit better what you mean by " STUDDER" , without actually being able to drive the car and feel what you are feeling it's going to be hard for any of us to predict what's going on

The A6 is a pretty reliable transmission and does not suffer from too many problems, if I had to guess what you are feeling is the Torque Converter locking and unlocking while in a steady state cruising speed which is normal as you might hit small inclines in the road that would cause it to unlock but it should not be noticeable.

Another guess might be that what you are feeling is a sparkplug misfiring

Why not take it somewhere and have a professional drive the car so they can feel what is going on and make recommendations on how to fix it

Dave

 

Dave,
Thanks for the reply,
As for the torque tube, yes i followed the TSB on that to drive it 10 miles with out the prop shaft clamp bolt finger tight. This was almost 2k miles ago.

As for the studder, it feels like the transmission is slipping at that 1100 rpm. When it does it, it goes up to about 1200, in this time the car might loose 1 mph, but once over 1200, it kicks back in and with then gain speed.

Now that you mention it, the converter un locking does make sense. and like i said its only at this low rpm while almost coasting, and then throttle slightly reapplied.

 

Yep I would bet that it's your converter , my A8 will do it once in a while and it is annoying, it's not slipping it's just the converter is not locked up and you are feeling the converter slip .

You can get any competent tuner to fix that if it bothers you real bad

Dave

 

"If i run in in paddle shift manual mode, the is does not repeat, i.e. no studder under the same condition." This statement proves that the AFM is operating going from V8 to V4 and back and forth. Search Forum for the 'Range device' for more details. It will solve this for you.

 

This has been working in my car for more than a year without any issues.

 

thanks for the feed back
i already have AFM disabled
i think it is the lock open vs open of the torque converter as mentioned above,