NemesisC5

Click the link I provided in post 8, it explains the procedure.

23/C8Z

wheels are more a product of low profile stuff sidewall run flats.

and there's absolutely nothing wrong with these torque converters

I have friends that run nines even some low nines on this torque converter even with the old fluid.

the problem lies within the fluid viscosity. The new fluid type has LV at the end for low viscosity all this was explained by my tech who's a Corvette Enthusiast and rebuilds every engine transmission rear end gear box under the sun. If your 8-speed ever blew up you would want this guy to rebuild your 8-speed as opposed to getting a factory reman unit I can guarantee that

I trust what he says, as well as the Corvette engineer at Carlisle in 2017 that told us about this fix

the formula has been changed the problem has been fixed now it's a matter of getting everyone to have this flush performed before their converters are eaten up by the thicker fluid

tertiumquid

Here you go:
2015 - 2017 Corvette: Shake and/or Shudder During Light Throttle Between 25 and 80 mp
2015 - 2017 Corvette: Service Bulletin: Shake and/or Shudder During Light Throttle Acceleration Between 25 and 80 MPH (40 and 128 KM/H) at a Steady State
Last Updated: Thu, Mar 2, 2017 at 1:45 PM
Some customers may comment on any of the following conditions:
A shake and/or shudder during light throttle acceleration between 25 and 80 mph (40 and 128 km/h) 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.
For 2015-2016 vehicles, shudder feeling is evident in both Drive and M7 mode.
For 2017 vehicles, shudder feeling is evident in both Drive and L7 mode.
Diagnosis Instructions
To ensure TCC shudder is diagnosed correctly, please drive the following schedule on a smooth road with transmission sump temperature between 122°F (50°C) - 158°F (70°C ).

Important: For some road conditions, it may be required to apply the brake pedal and throttle simultaneously to stay within desired engine torquerange, and engine/vehicle speed ranges.

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).

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 torqueconverter 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 fluid flush procedure corrective action described below should be performed.

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 clutchdisabled (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 in 8th gear in the application specific condition above. Minimize extraneous vibration input by testing on a smooth road and correct any other known vehicle vibration issues (tires, brakes, etc.) before conducting test. If TCC Shudder is present, a vibration peak will appear (highlighted by arrow below) within +/-2 Hz of the frequency listed in the table above. TCC Shudder vibration frequency should remain constant in 8th gear as indicated in the above table. If the vibration frequency follows vehicle speed or enginespeed, then it is NOT TCC Shudder.


Service Procedure
Important: Requires Mobil 1 Synthetic LV ATF DEXRON HP (GM Part No. 19353429, in Canada 19353430).

Note: U.S. dealers must order the Mobil 1 Synthetic LV ATF DEXRON HP fluid through your local General Motors oil distributor. Canadian dealer must order through CCA.

Step 1: Cooler Flush, Drain, Clean pan/magnet, Replace Filter (If needed), Oil Fill, & Circulate New Fluid

Note: The Transmission Fluid Cooler Flow Test and Flushing procedure can be located by building the vehicle in SI, select Transmission, TransmissionCooling, Diagnostic Information and Procedures. Select the appropriate transmission.

1 a.) Flush the cooler lines and cooler, refer to SI for proper procedure.

Note: DEXRON VI transmission fluid may be used to flow and flush the transmission cooling system. Compressed air should be used to remove any residual fluid from transmission cooler lines.

1 b.) Remove the transmission fluid pan and drain transmission fluid following SI procedures for the application you’re working on. Discard all oil.

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 (L83, L86)” and “Engine Coolant/Water in Transmission.”

1 c.) Clean the pan/magnet if any metallic particles present and replace transmission filter if debris is found.

1 d.) Install the transmission fluid pan and refill with new transmission fluid using enough volume to have oil come out of oil level check plug.

Important: Operate the vehicle on the hoist for 10 minutes. Cycle through all forward gear ranges, Reverse and Neutral.

 

Step 2: Drain, Oil Fill, & Circulate New Fluid

2 a.) Remove the transmission fluid pan and drain transmission fluid again. Discard all oil.

2 b.) Install the transmission fluid pan and refill with new transmission fluid using enough volume to have oil come out of oil level check plug.

Important: Operate the vehicle on the hoist for 10 minutes. Cycle through all forward gear ranges, Reverse and Neutral.

 

Step 3: Drain, Oil level Set, and Drive to Evaluate

3 a.) Remove the transmission fluid pan and drain transmission fluid again. Discard all oil.

3 b.) Install the transmission fluid pan and refill with new transmission fluid following the “Fluid Fill Procedure” in SI to obtain correct fluid level.

The shudder should be improved after the completion of this triple flush procedure.

Note: Shudder should improve directionally right away, but for full affect the vehicle may need to be driven up to 200 miles (322 km). and at least two cold to hot drive cycles before determining if the fluid flush corrected the condition or not. Do not re-evaluate vehicle for additional customer shudder concerns until the vehicle has been driven 200 miles (322 km).

Warranty Information
For vehicles repaired under the Bumper-to-Bumper coverage (Canada Base Warranty coverage), use the following labor operation. Reference the Applicable Warranties section of Investigate Vehicle History (IVH) for coverage information.

LABOR OPERATION

DESCRIPTION

LABOR TIME

8480478*

Flush and Drain Fluids for Transmission Shake and/or Shutter Repair

Use Actual Clock Time

*This is a unique Labor Operation for Bulletin use

FrcFed8

tertiumquid

I believe it's still active but I don't have the number. I'm seeing the dealer today and will find out if I can get that info and post it.

FrcFed8

MidLife+

Don't want to be a party pooper but....
On my 2016 Z06 A8 I have had the flush, torque converter replaced and now they have ordered me a transmission valve body. It still shudders in manual mode (7th gear) and shifts very hard from 1st to 2nd and the downshift is extremely delayed and hard.

I am second guessing my C6 GS trade for the C7 Z06!!!

gbmidyear66

Agreed - it is NOT just an AFM issue, it happens in V8 mode (well at least the dash indicator says its in V8 mode) on light accel at highway speeds. Changing the Torque Converter is no panacea either (had that done in the first 500 miles of ownership, better but still noticeable). The new fluid also reduced the shudder (at least in my case for the last 4,000 mikes since I had it replaced). Sadly, they really just don't seem to have a clean and permanent fix for this issue.

GhostBluZ06

Hey guys, Im getting my car back this evening. So they didnt touch my cars TC at all nor did they do the flush. Instead i was given pretty much a trans tune/ recalibration. I have to drive it for a few 100 miles to let them know if this fixes it...... if not they are going in my trans.

23/C8Z

They'll also be additional issues. Not a 1 stop fix but the 99% majority is the formulation and or viscosity of the fluid.

quicksilver2k1

I have a question.
Would a after market converter be a better solution.
I have had the triple flush and it has not worked.
Reading that the problem is coming back after a replacement is done makes me wonder if the aftermarket convertor would be the answer.

383vett

GeorgeR_Zed06

A lot of people including service techs are calling the sound of the AFM/DOD engagement-disengagement, a shudder. Disable AFM.

tertiumquid

True, but that's not the real problem. A lot of people think the V8/V4 thing is what's happening and in some ways, it feels similar. But, once your TC is damaged by the oil issue, the AFM disable (like with a Range module which works great) won't solve the shudder. As others have posted, apparently the original problem was the viscosity of the oil used in the 15-17 cars. You'd think after a few years of this experience with all GM cars using the A8, it would have been well understood and solved but apparently not. My 2016 is going back in on Oct 3rd for a second diagnosis after the problem was still there after the triple flush procedure. I hope a new TC will get this thing fixed. When you punch it, it will still go like a rocket without any problem but that damned shudder is really annoying.

GeorgeR_Zed06

yeah I can see that happening too. it's a good thing mine doesn't display any of these issues, if it did, I would ditch it for a new ZL1.

tertiumquid

What year is your Z?

23/C8Z

how many miles are on your ZO6?

tertiumquid

Just coming up to 11K

23/C8Z

I'm at 5800. Hoping I got it before it got beyond the point of no return lol. Drove it today on the highway no shudder. Like waiting for the other shoe to drop! But that feeling will wear off....or if it comes back i'll get the converter done.

tertiumquid

Somebody else posted in another thread that to be smart, get your fluid changed by the triple flush now before you have any symptoms. If the original fluid composition was the culprit then this would be a good idea but you'd probably have to pay for it unless you could convince your friendly dealer to put it through under a complaint situation that they verified..While I can see there's substantial indication this was the cause< I don't know if this will avoid the problem for you in the future. If I had the opportunity, I'd have the flush done. It's a roll of the dice.