Found this online today.
https://www.midenginecorvetteforum.c...ission-shudder
New Fix A8 Transmission Shudder
12-13-2018, 02:30 PM
GM has come out with a additional/separate fix for the Z8’s transmission shudder, one different front the torque tube clutch replacement. If you are having an A8 trans issue, this could be very helpful information for you. Unfortunately, with all new procedures/parts, it is not yet available. Hopefully, this will help those of you who have been having this issue.
What has been so interesting to many who have been following this, is that over 90% of all users with A8’s have not have an issue, but others have had it, and unfortunately, some more than once.
Originally posted by
GM Technical Assistance Center
8 Speed Torque Converter Shudder – New Service Procedure and New Mobil 1 Synthetic LV ATF HP Fluid Regional Rollout
GM CUSTOMER CARE & AFTERSALES
URGENT - DISTRIBUTE IMMEDIATELY DATE 12/12/2018 SUBJECT 8 Speed Torque Converter Shudder – New Service Procedure and New Mobil 1 Synthetic LV ATF HP Fluid Regional Rollout MODELS 8L45 and 8L90 Applications TO All Cadillac, Chevrolet and GMC Dealers ATTN Service Manager, Service Director, Shop Foreman, Service Technician, Parts Manager, Parts Counter Personnel, Warranty Administrator, General Manager
A new transmission fluid exchange procedure and new formula of Mobil 1 Synthetic LV ATF HP transmission fluid is being released to address torque converter shudder on 8L45 and 8L90 applications. The procedure and new transmission fluid is being rolled out regionally due to the limited availability of both the new transmission fluid and tool kit availability. The dealer rollout was determined by paid warranty claims from TSB 16-NA-175. It is anticipated that the new transmission fluid and tool kit will be available nationwide by late January or early February 2019. Once the new transmission fluid and tool kit is available the detailed service procedure will be loaded into GM Service Information (SI) as a Technical Service Bulletin (TSB). TSB's 16-NA-175 and 18-NA-177 will be eliminated from SI. An additional Global Connect Message will be sent to announce these changes.
Selected dealers will receive a separate Global Connect Message this week advising how to obtain the new Mobil 1 Synthetic LV ATF HP transmission fluid, delivery of the no charge tool kit from Bosch and detailed service procedure.
The new fluid exchange procedure will require the use of the existing DT-45096 TransFlow machine and tool kit. The tool kit will ship from Bosch at no charge.
The December 2018 Emerging Issues Broadcast, course number 10218.12V will be available through the Center of Learning on Thursday, December 13. The broadcast contains a video demonstrating the procedure on a Chevrolet Colorado and details on the new Mobil 1 Synthetic LV ATF HP transmission fluid.
The detailed service procedure may seem complicated at first review. However, we are confident that once you've completed the procedure you will find it relatively easy.
Proper Diagnosis: Sometimes shudder is not caused by the torque converter clutch (TCC). In some instances, shudder is fish bite, chuggle, surge or vibration. Utilizing the GDS and or the PICO Scope will help confirm the issue is TCC shudder. We have seen cases of suspected TCC shudder turn out to be engine performance, tire/wheel vibration or a driveline vibration.
Please do not contact the Technical Assistance Center (TAC) seeking information on when the new Mobil 1 Synthetic LV ATF HP transmission fluid and tool kit will be available nationwide. TAC does not have any additional information.
For those dealers that are not among the initial selected group. Please continue to follow 16-NA-175 and 18-NA-177 until the new service procedure is available nationwide. We are working diligently to get the new service solution available to all dealers and will advise through an additional Global Connect message once available.
Thank you for your cooperation.
GM CUSTOMER CARE & AFTERSALES
Document :
https://dealer.autopartners.net/portal/uscontent/headlines/Pages/GCUS-9-7040.aspx 8 Speed Torque Converter Shudder – New Service Procedure and New Mobil 1 Synthetic LV ATF HP Fluid Regional Rollout