I took mine in yesterday. I simply told the service writer that the car was shuddering under light acceleration, like driving over rumble strips even though the road is smooth, and most noticeably in V4 mode in 7th or 8th gear, and the RPMs were fluctuating by 100. Would calm down if I put it in manual mode. They were aware of the TSB.

A few minutes later the Corvette tech walked by and we chatted about it. He said that the new fluid is the fix. No one has come back for shudder after the new flush. They drove it to verify the shudder. Their transmission guy road tested after the flush and says all is well. Work done under warranty. I pick it up tonight, fingers crossed.

 

Last I knew, GM was only doing a "single flush," with the new fluid, not the triple flush they started out with.

Can anyone confirm it is back to the triple flush?

 

Mine was done under warranty last week, work sheet shows the Tech removed pan and refilled three times.
I’m pretty sure that’s what the July bulletin says to do but don’t have a copy with me.

 

Hello all,

I was having other updates done on my car and since I was aware of the trans problem I just stretched a little and said you know I think this thing is surging a little bit ?

Would you guys be so kind as to look into the TSB's and I understand there's a new fluid? I really like it changed with the triple front flush procedure if you would be so kind, as I would like to make sure the lines and coolers are flushed as well.

They decided to do that for me, It might've had something to do with the fact that was spending money on a bunch of other things including the mag ride update !!!

My advice, we know the problem, tell a story and get it fixed. These are expensive cars were not hurting GM there's an issue with the hydroscopic fluid.

There's my two cents hopefully someone will find it worthy of the $600 it's saved me :-)

Kevin

 

Have just finished my third careful reading of this thread and can't find the 18-NA-355 with the July 2019 revision. The one with this number I did find is undated and describes the required diagnostic procedure. I can not find 19-NA-121 at all.

Easy for me to claim ignorance here. My 2019 Stingray is about 1 month old. I would like to have these 2 documents in hand when I go into a dealer for this service. I well may be doing the search wrong and if someone can also fill me in on the specific site to search, it would be appreciated.

 

I can’t find the July 2019 TSB either. I hope someone will post it.

 

It would indeed be nice to have the latest version of the bulletin in hand, both for our own entertainment and to “educate” a reluctant dealer. But these things often take a while to migrate from the GM system to the internet.
Lots of dealers have done probably hundreds of flushes recently without the picoscope or any other diagnosis except the customer telling them of the problem. If they aren’t following the official procedure, GM won’t pay them. If your dealer balks and claims they can’t find the new July (or newer) version , time to find a dealer who knows how to do their job.

 

I guess I should be good then.

 

I took my beautiful girl to the dealership today looking for the triple flush. Without the July 2019 revision of the 18-NA-355 TSB, all I could do was parrot the magic words and hope for the best.

That didn't work out for me. They test drove the vehicle, claimed no shudder, and "programmed TCM with the latest calibrations, warranty claim code 18YN24490124."

I know I've been told to "find a dealer who knows how to do their job", but that's easier said then done. Now, I will have to schedule with a more distant dealer, and beg a ride from a fellow employee that will go out of their way to give me a ride back-n-forth. Without the TSB, you are at the whims of the dealer & his mechanic.

Please! Someone reading this, help us find the updated TSB!

 

Here ya go.... I cut and paste the part applicable to Corvette.


#18-NA-355: Shake and/or Shudder During Light Throttle Acceleration Between 25 and 80 MPH (40 and 128 KM/H) at Steady Speed - (Jul 29, 2019)
Subject: Shake and/or Shudder During Light Throttle Acceleration Between 25 and 80 MPH (40 and 128 KM/H) at Steady Speed



Corvette

2015 to Feb. 1, 2019 LT1, LT4




Fluid Exchange Procedure - Corvette and CT6Important: The Drain and Fill Procedure Will Need to be Performed Three Times.


Important: This procedure must be followed as published. The exchange process is required to obtain proper level of new blue label Mobil 1 Synthetic LV ATF HP fluid. Intermixing of other types of transmission fluid or aftermarket additive packages will result in a low concentration level of new fluid and will not provide satisfactory results.

1. Fill the DT-45096 with 24 quarts of HP fluid.
2. Raise the vehicle.
3. Using care, remove the transmission oil pan and drain the transmission fluid.
4. Install the transmission oil pan.

1. Install the DT-45096-31 adapter (1) to the DT-51190 fluid fill adapter (2).

1. Remove the level set plug (1) from the transmission oil pan.

Important: DO NOT over tighten the DT-51190 as it can be damaged by excessive torque. Do not exceed 9 Y (80 lb in).

1. Install the DT-51190/DT-45096-31 assembly and hand tighten.
2. Connect the TransFlow fluid feed (supply) line (3) to the DT-45096-31 adapter (2).
3. Connect the DT-45096 TransFlow to the vehicle battery 12 volts and connect shop air to the air connection.
4. Switch the DT-45096 TransFlow to Flow and fill the transmission with 8 quarts of transmission fluid.
   1. Switch the DT-45096 TransFlow to idle.
5. Partially lower the vehicle and run the transmission through all 8 forward gears, Reverse and Neutral.
6. Repeat steps 2-4 and 9-10 for 2nd drain and fill.
7. Repeat step 2-3, clean the transmission oil pan and magnet, repeat step 4 and step 10-11.
8. Perform the Transmission Fluid Level and Condition Check outlined below in this procedure:
   1. Get the transmission fluid temperature to the proper temperature.
   2. Raise the vehicle and remove the DT-51190/DT-45096-31 assembly.
   3. Install the level set plug.
      Tighten
      TightenTighten the plug to 9 Y (80 lb in).
      

The TCC shudder condition should be directional improved immediately after the fluid exchange procedure. It may take up to 320 km (200 mi) for the TCC shudder condition to be eliminated. It is not a requirement for the dealer to drive the vehicle 320 km (200 mi). The customer should be advised that the full effect will take up to 320 km (200 mi) and a minimum of two cold to operating temperature drive cycles.

 

Sorry Friend, you missed the point. We can already get the old copies of TSB 18-NA-355 with full instructions. What we need, is a copy of the July 9, 2019 Revision to eliminate the diagnostics portion within the TSB, and the labor times have been updated to reflect the removal of the diagnostic procedures.

 

I receved my 2019 Z51 stingray in October of 2018 and have 8000 miles on it. I would like to find and purchase the Range device you speak of. Can you tell me where you purchased your device, price and is it easy to install?
If you want to PM me with the info, I will check the mailbox.

Thanks for your help.

 

Buy from the company that makes them. You will be sure to get one that is up to date and not a counterfeit.
https://rangetechnology.com/afm-disabler/

 

+1. That is what I did. Could not be easier to install. Just plug it in to the OBDII port and you are done.

 

Just ordered one yesterday, does this eliminate the need for a triple flush?

 

GM would tell you that the triple flush is the real solution and the Range is unnecessary.
And some people have reported getting shudder even with the Range.

In in your position I’d get the flush and then install the Range.

We got the free flush at 30k miles last month on our 2017, no shudder before or after. We have never used the Range and most of our driving is highway miles in Auto, so it goes into V4. Nobody seems to know why some cars have the problem and others don’t.

 

I let my 2011 Corvette GS go about a month ago and picked up a 2017 Corvette GS with a little over 2K miles. After thinking that I was feeling a very slight vibration, I started to look at the tachometer more as I drove and noticed an occasional 100-200 rpm bump when shifting from V8 to V4 mode. I decided to look at comments from other C7 owners on this forum to see what others had experienced...and many recommended the Range Device to keep the car in V8 mode. For the record...I do not like AFM. I purchased the latest edition from the manufacturer of the device, plugged it in, and noticed an immediate improvement. I still sometimes detected a very slight vibration so I took the car back in to the a Dealership and had them to do a Road Force balance at my expense because I suspected the tires were slightly out of balance. They found that both of my rear rotors were slightly out of spec and replaced them both under warranty. After a week I went back in an said I still feel an occasional low level vibration on a smooth road but things have improved. They suggested I make an appointment to come back in and let them do a triple flush with the “magic fluid” and even suggested they might replace my tires all under warranty. With that said, I have now driven the car another 1000 miles plus and I am watching it closely. The triple flush was completed about 300 miles ago and I’m not sure if it changed anything or not. I really like the car overall, I just hope I don’t have some of the major problems with my A8 that others have had. For the record, the build date on my 2017 model car was 12/16, and it still looks mint and smells like new inside! I’m keeping my fingers crossed...

 

Well after two triple flushes, the shudder is back. Not as bad as when it first happened but it takes the fun out of driving thats for sure. My power train warranty expires at the end of next month so I am back in communication with my dealer to see what they plan on doing to correct it. I'm thinking if two flushes with 48 quarts of fluid didn't do the trick either they didn't actually do the triple or there is something going on with my torque converter.

 

^^^
This might be a good time to have the dealer do the diagnosis with pico scope that used to be mandatory.
Since the current "just throw fluid at it and that's good enough" didn't work, they need to be sure exactly what's causing the problem.
You want them to acknowledge that there is a problem while still under warranty.
Best of luck to you.

 

I think that in cases where someone has had the shudder for a very long time, the damage to the torque convertor has been done and getting the triple flush done will not reverse that damage.