2017 A8 Z06 Torque converter lock up and unlock switch

[dwiall]

I have a 2017 A8 Z06 and would like to unlock the torque converter to see if a shudder I have goes away. Also, is there a way to log all the channels/tables. I would like to record them and see if I can see anything funny that may relate to the shudder. What happens is under slight acceleration the car will act like it is missing. I had a 2016 with same problem and GM gave me a 2017 and it is doing the same thing. They think it is the torque converter being locked and I am feeling just the motor's running imperfections. I had the field rep along on the 2016 and he unlocked the converter and the shudder pretty much went away. Thanks in advance.

[Higgs Boson]

have you licensed the vin so you can set the converter to unlocked?

[dwiall]

have you licensed the vin so you can set the converter to unlocked?

Yes I have registered it, just need to know where the toggle is. I new to all this and learning as we all were at one time.

Thanks

[Sam88gta1]

Turn it off with the VCM Scanner. Its much easier that way. TCC.png

[dwiall]

Turn it off with the VCM Scanner. Its much easier that way. TCC.png

Thank you. What a great reply. Took car out and turned it on and off and you can tell the difference, hardly any shudder when I unlock it. I suppose it will heat up quicker now that the plates are slipping. I'll just leave it locked up. Nice to finally know what might be going on. Can you change the point at which it locks up?

[Higgs Boson]

cool, last time I tried the VCM controls on a C7Z they didn't work.

yes go in the tune in the Transmission section and the TCC tab

[Redline MS]

#PIP5337H: Shake Or Shudder On Acceleration - (Dec 21, 2016)
Subject: Shake Or Shudder On Acceleration

Models: 2015 - 2016 Cadillac Escalade, Escalade ESV built prior to 11/01/15
2015 - 2016 Chevrolet Corvette, Silverado built prior to 11/01/15
2015 - 2016 GMC Sierra, Yukon, Yukon XL built prior to 11/01/15
Equipped with 8L90 Automatic Transmission (RPOs M5U) and the 6.2L (RPOs L86 and LT1)
Note: This information does not apply to Silverado and Sierra models with the 5.3L (RPO L83).
Please refer to bulletin 16-NA-175 for all other vehicles equipped with the 8L90 automatic transmission RPO (M5U) with shudder concerns.
This PI was superseded to remove part numbers. Please discard PIP5337G.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern
Some customers may comment on any of the following conditions.

A shake and/or shudder during light throttle acceleration between 48 and 104 km/h (30 and 65 mph) steady state driving when transmission is not actively shifting gears.

A shudder feeling that may be described as driving over rumble strips or rough pavement.

A shudder feeling that is evident in both Drive and M7 mode.

Recommendation/Instructions
To ensure TCC shudder is diagnosed correctly, please drive the following schedule on a smooth road with transmission sump temperature between 50?C (122?F) - 70?C (158?F).

Important: For some road conditions, it may be required to apply the brake pedal and throttle simultaneously to stay within desired engine torque range.

Press and hold the tow-haul mode button for 5 seconds to disable grade braking to prevent downshifts during test.

Run the following tests for 3 operational modes:

A. Normal Operation (GDS2 for viewing only).

B. GDS2 Commanding TCC in Disabled Operation. (TCC Open).

C. GDS2 Commanding TCC in Enabled Operation. (TCC Locked).

TEST:

Drive the vehicle in 8th gear, V8 mode, with a transmission input speed of 1,050–1,300 rpm with (approximately 64-89 km/h (40–55 mph)) constant throttle input, and engine torque 200-375 Nm.

To confirm TCC shudder, the vibration concern must be created in normal operation (Mode A) of the test.

If the concern is gone with the torque converter clutch disabled (Mode B, TCC Open) and is gone when the torque converter clutch enabled (Mode C, TCC Locked), the vibration root cause is TCC shudder and the torque should be replaced.

If the concern is not present in Mode A, then the vibration concern is not TCC shudder.

If the concern is still present with the torque converter clutch disabled (Mode B) or with the torque converter clutch enabled (Mode C, TCC slip speed at zero), the root cause of vibration is NOT shudder.

Vibrations not identified as shudder should be further investigated using the “Vehicle Vibration Diagnosis in SI as a starting point.

The use of the PICO scope and NVH software can be used to confirm TCC shudder, Engine, Tire or Driveline component related conditions.

To confirm TCC shudder record the PICO scope data while driving the vehicle in 8th gear, in V8 mode, with a transmission input speed of 1,050–1,300 rpm At 40 to 55 MPH (64-89 km/h) at constant throttle input, and engine torque 200-375 Nm.

The disturbance will display as unknown and will be around 26 Hz at 16 to 24 mg as shown in the illustrations below if the concern is TCC shudder.

Note: If an engine 2 (E2) disturbance is noticed in the graph the engine most likely went into V4 mode.

Object ID: 4620118Click here for detailed picture of the image.
In the above illustration frequency and default view have been selected.

Object ID: 4620120Click here for detailed picture of the image.
Additionally the following should be performed as well during the torque converter replacement process.

Flush the cooler lines and cooler using DT-45096 transmission oil cooling system flush and flow test tool.

Use compressed air to remove any residual fluid from the cooler and lines.

Remove the transmission fluid pan and drain transmission fluid.

Note: If you find that the fluid is cloudy, milky, or appears to be contaminated with water or engine coolant, DO NOT proceed with below steps.

Follow Both SI Procedures for "Cooling System Leak Testing and "Engine Coolant/Water in Transmission."

Install a new transmission filter, clean pan and magnet.

Install the transmission fluid pan and refill with new transmission fluid following the fluid fill procedure in SI to obtain correct fluid level.

Note: Only DEXRON?HP Fluid should be used. The US part number for the DEXRON?HP Fluid is 19353429, P/N (19353430) in Canada.

Note: US dealers must order The DEXRON?HP fluid through your local General Motors oil distributor. Canadian dealer must order through CCA.

Important: Under certain load conditions a minor chuggle/shudder feel may be felt in the passenger compartment due to natural engine frequencies or Active Fuel Management (AFM) transitioning from 8 cylinder to 4 cylinder and back to 8 cylinder.

It may be necessary to compare the operation of the vehicle to a known good unit under the identical driving conditions as the operation may be characteristic.

In the event that the customer returns for a confirmed torque converter shudder after replacing the torque converter please follow bulletin 16-NA-175.

Warranty Information
For vehicles repaired under warranty use:

Labor Operation
Description
Labor Time
8480518
Replace Torque Converter, Filter and
Corvette
13.6
Flush Cooler Lines
4wd Truck and Utility
6.5
2wd Truck and Utility
5.6

[dwiall]

Thanks for the bulletin. Dealer changed TC, transaxle, and axels on my 2016 with no change. I've driven a few and they have all done it so it may just be characteristic of the car as mentioned in the bulletin. Unlocking the TC does help. They have really added a lot of info to the bulletin compared to the original. Original was about five lines long.

[Higgs Boson]

Thanks for the bulletin. Dealer changed TC, transaxle, and axels on my 2016 with no change. I've driven a few and they have all done it so it may just be characteristic of the car as mentioned in the bulletin. Unlocking the TC does help. They have really added a lot of info to the bulletin compared to the original. Original was about five lines long.

They keep the converter locked as much as possible so what that means is that sometimes it is not possible. Compared to older cars that kept the TC unlocked a lot more you are going to feel it locking and unlocking depending on torque demand, RPMs, etc. Basically they used to be unlocked all the time except at cruise so you never felt so much activity.

So yes, forcing it to unlock will calm it down but it doesn't mean you have found the cure to the A8 TC. I used to run it unlocked all the time except for cruise since I wanted to go back to the old ways but I got tired pretty quick of the RPMs zinging up before I would get acceleration every time I wanted to roll into it a bit. I like it locked better, it acts more like a stick.

I think GM just needs to source a stronger converter and apply more TCC pressure.

[veee8]

We really need tables similar to the A6's to increase TCC pressure on the A8. If you log it, it has very light pressure. Likely the reason the aftermarket converters have been burning up clutch discs.

[8850]

Have not noticed this on my 2017 Z06 A8. Perfectly smooth in all gears.

[dwiall]

That was going to be my next question is if there is any kind of control we may have on line pressure

[dwiall]

We really need tables similar to the A6's to increase TCC pressure on the A8. If you log it, it has very light pressure. Likely the reason the aftermarket converters have been burning up clutch discs.

I hate to be a pain but where do I see the pressure in a logged file? I would like to start comparing line pressure of mine with those that say there's is silky smooth. I have driven five different Z's and they have all done it.

Also, is there some tutorials on the HPtuners use and how to navigate through all the screens and features? Hate to keep asking basic questions.

[veee8]

If the parameter was not logged at the time of the log, you can't go back and add it. You can add it to your channel list for logs that you take from then on out.
Select a spot on your channel list, right click, add parameter and select the PID you would like.
There are many tutorial write ups regarding the scanner in the scanner sub-forum.