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Discussion Starter #1 (Edited)
Thanks to Ken Fichtner at Denny Menholt Chevrolet, we have this recently released Corvette roof noise bulletin.

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PIP5260B: Active Rev Matching Inoperative P0731

Thanks to SK360 for supplying:

#PIP5260B: Active Rev Matching Inoperative P0731 - (Sep 1, 2015)
Subject: Active Rev Matching Inoperative P0731 999999995
Models: 2015 Chevrolet Corvette
With manual transmission RPO MEL
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern
Some customers may comment that the Active Rev Matching feature is inoperative and upon further inspection technician may find a P0731 stored in the engine control module.

Recommendation/Instructions
If you should encounter this condition on a 2015 equipped with a MEL RPO transmission update the calibration in the ECM as there was software released to correct this condition.

Warranty Information
For vehicles repaired under warranty use:

Labor Operation

Description

Labor Time

2810095

Powertrain Control Module Engine Reprogramming with SPS

Use Published Labor Operation Time
 

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Thanks to elegant for the following regarding 2016 Heating/Cooling seats:

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A8 Transmission Adaptive Functions

The following TSB is thanks to member Kawika:

Document ID: 4726097
#14-07-30-001G: Information on Transmission Adaptive Functions and Correcting Low Mileage Harsh Shifts - (Mar 3, 2017)
Subject: Information on Transmission Adaptive Functions and Correcting Low Mileage Harsh Shifts
Models: 2015 Chevrolet Corvette
Equipped with 8L90 Automatic Transmission (RPO M5U)
Attention: This Bulletin also applies to any of the above models that may be Export vehicles.
This Bulletin has been revised to update the Models section and redirect all trucks and utility applications to a new bulletin. Please discard Corporate Bulletin Number 14-07-30-001F.
Important: For all truck and utility applications with the 8L90 automatic transmission, refer to 16-NA-411 for the latest information for correcting low mileage harsh shifts. This bulletin only applies to the Corvette with 8L90 automatic transmission.
Some customers may comment on low mileage vehicles equipped with the 8L90 automatic transmission with shifts that feel too firm (harsh), slips or flares. Customers should be advised that the transmission makes use of an adaptive function that will help to refine the shift feel and improve shift quality while driving. Clearing the shift adapts without performing a Service Fast Learn should not be considered a repair procedure as the transmission will simply relearn the previous settings.
Correction
The following should be used to determine what steps should be followed within this document.
The 8-Speed transmission utilizes a total of 5 clutches to obtain all the ratios. Utilize the chart within this document to determine which clutch may require additional adaptive learning.
· If a transmission assembly, valve body, torque converter, TCM, or any repair regarding shift quality was required, reset the adapts using Service Fast Learn. Evaluate the shifts and further learn pressures and volumes if required.
· If a customer has a specific shift concern, the Service Fast Learn should be skipped. Complete the driving learn procedure to further learn pressures and volumes for the complaint shift.
Transmission Adaptive Functions
The Hydra-Matic® 8-Speed RWD transmission utilizes a line pressure control system during upshifts to compensate for new transmission build variation as well as the normal wear of transmission components. The variation experience on a new and normal wear of the apply components within the transmission over time can cause shift time (the time required to apply a clutch) to be longer or shorter than desired.
In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various pressure control (PC) solenoids to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as "adaptive learning" and it is used to ensure consistent shift feel plus increase transmission durability.
The TCM monitors the A/T input speed sensor (ISS) and the A/T output speed sensor (OSS) during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the
corresponding PC solenoid signal to maintain the set shift feel. The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle.

How to Adapt Your Transmission
Transmission adapts can be reset and relearned on most vehicles through GDS 2 by using the Transmission Service Fast Learn procedure. This procedure is completed in the service stall and no vehicle driving is required.
To complete the Transmission Service Fast Learn procedure, enter GDS 2 Diagnosis and navigate to:
- Module diagnostics
- Transmission Control Module
- Configuration / Reset Function
- Transmission Service Fast Learn
Transmission Service Fast Learn is the recommended method to reset and relearn the adapts. This procedure is available on all trucks and SUVs and on Corvettes built on September 29, 2014 and later. For Corvettes built before September 29, 2014 the Transmission Service Fast Learn will be available if the TCM calibration is updated to the latest available on TISWeb.
When the Service Fast Learn is complete, perform a test drive and note any soft or harsh shifts.
To improve these complaint shifts, locate the clutches that need to be learned in the following table below, and perform the required learning procedure for each clutch listed below the chart. Execute the steps below with the vehicle warmed up on a smooth level road. The driver may observe a brief pulse behavior or firm shift feel while the transmission is optimizing the clutch learn characteristics.
Note: I he transmission fluid temperature must be between 35'L (9b`A- ) and 9.5°C (203°F). Drive
vehicle under normal conditions until this temperature range is achieved. If temperature is outside this range the clutches will not be learned.
Learn These Clutches
I.J1 I C1.
a C Shift
rCCI Applying Clutch Releasing Clutch
1-2 C4 C3
2-3 C3 C1
3-4 C5 C3
4-5 C3 C4
5-6 C4 C2
6-7 C1 C4
7-8 C4 C3
3-1 Cl C4
2-1 C3 C4


N-D C3 - Perform garage shift adaptive learning
N-R C5 - Perform garage shift adaptive learning
Power Downshifts Just perform the shifts and they will adapt

Note: If the harsh shift is noted when the vehicle is coming to a stop and shifting into 1st gear, this downshift is most likely a 3-1 shift.
Note: This sequence is MY 2015 specific and varies from MY 2016. The following adaptive learning procedure was developed to further learn clutch pressures and volumes required for specific shifts. To expedite the learning process, it is fecommended to utilize a road with minimal traffic volume that has as smooth and level surface as possible.
To Learn Cl (For 6-7 or 3-1 Shift) 1. Pressure & Volume Learns:
Note: It is recommended to utilize a road with a speed limit between of 30-45 mph (48-72 km/h) fo this procedure.
Shift the transmission into 6th gear with the PRNDM in the M position. Obtain an engine speed between 1000 and 1600 rpm. Maintain this condition for a total of about 5 miles (8 km). Cruise control may be used and has been found to result in faster learning of the clutch values
To Learn C2 (For 6-5 Shift)
1. Pressure Learn:
Note: : It is recommended to utilize a road with a speed limit 40-45 mph (64-72 km/h) for this procedure.
Perform 15 normal mode 6-5 coast down shifts (zero/light brake) to learn the C2 Return Spring pressure.
2. Volume Learns:
Shift the transmission into 8th gear with the PRNDM in the M position. Obtain an engine speed between 1000 and 1750 rpm. Maintain this condition for a total of about 5 miles (8 km). Cruise control may be used and has been found to result in faster learning of the clutch values
To Learn C3 (For 2-3, 4-5, or N-D Shift)
1. Pressure Learns:
Perform 15 normal mode 8-7 coast down shifts (zero/light brake) to learn the C3 Return Spring.
2. Volume Learns
Note: It is recommended to utilize a road within a Business Park or similar area, where it is safe to drive at very slow speeds of approximately 5-25 mph (8-40 km/h).
Shift the transmission into 4th gear with the PRNDM in the M position. Start a slow acceleration at about 1,100 rpm and maintain the slow acceleration until you reach about 1,500 rpm. Once you reach 1,500 rpm, go back down to 1,100 rpm and repeat the slow acceleration up to 1,500 rpm. Repeat this 15 times.
Important: If rpm's drop below 1,100 rpm vehicle will downshift into M3 and pause learning process. If this occurs please accelerate and tap back into M4 and start counting from where you left off. Additionally while watching the tachometer and applying a constant throttle. You'll see tachometer rpm's increase rapidly and then once adapt process starts rpm ramp rate will decrease and you'll feel the vehicle having a tie-up type feel.

To Learn C4 (For 1-2, 5-6, or 7-8 Shift) 1. Pressure & Volume Learns:
· Shift the transmission into 7th gear with the PRNDM in the M position. Obtain an engine speed between 1000 and 1750 rpm. Maintain this condition for a total of about 5 miles (8 km). Cruise control may be used and has been found to result in faster learning of the clutch values
To Learn C5 (For 3-4 or N-R Shift) 1. Pressure & Volume Learns:
Note: it is recommended to utilize a road within a Business Park or similar area, where it is safe to drive at very slow speeds of approximately 5-25 mph (8-40 km/h).
· Shift the transmission into 3rd gear with the t'RNDM in the M position. Start a slow acceleration at about 1000 rpm and maintain the slow acceleration until you reach about 2500 rpm. Once you reach 2500 rpm, go back down to 1000 rpm and repeat the slow acceleration up to 2500 rpm. Repeat this 15 times.
Important: While watching the tachometer and applying a constant throttle. You'll see tachometer rpm's increase rapidly and then once adapt process starts rpm ramp rate will decrease and you'll feel the vehicle having a tie-up type feel.
Power Downshift Adaptive Learning:
Starting with the vehicle operation in 8th gear, slowly apply pressure to the accelerator pedal until downshift occurs. Repeat as necessary in each gear (8, 7, 6, 5, 4, 3 and 2).
· This procedure will learn the off-going clutch adapts for desired power downshift control. Garage Shift Adaptive Learning (For N-D or N-R Shift)
N-D - Perform C3 learn above and in addition perform several N-D shifts within the complaint temperature as described by the customer.
N-R - Perform C5 learn above and in addition perform several N-R shifts within the complaint temperature as described by the customer.
Warranty Information
For vehicles repaired under the Powertrain coverage, use the following labor operation. Reference the Applicable Warranties section of Investigate Vehicle History (IVH) for coverage information.

Labor Operation Description Labor Time
8480318* Drive Learn Procedure Use Actual Clock
Time
*This is a unique Labor Operation for Bulletin use only.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to Inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist In the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition Is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

Document ID: 4605342
#16-NA-361: Information on Transmission Harsh 1-2 Shift Upon First Start Up/Shift of the Day Under Light Throttle -(Apr 6, 2017)
Subject: Information on Transmission Harsh 1-2 Shift Upon First Start Up/Shift of the Day Under Light Throttle
Brand: Model: Model Year: VIN: Engine: Transmission:
from to from to
Cadillac ATS 2016 2017 Automatic 8L45, 8L90 (M5T, M5N, M5U, M5X)
CTS
Models
CT6
Escalade
Models 2015
Chevrolet Camaro 2016 2017
Corvette 2015 2017
Silverado
GMC Sierra 2015 2017 Automatic
8L90 (M5U,
M5X)
Yukon


Involved Region or Country North America and N.A. Export Regions
Condition Some customers may comment that the transmission exhibits a harsh 1-2 shift on the first shift of the day, typically under light throttle.
Cause This condition is due to the initial clutch fill time of the 2-3-4-6-8 (C4) clutch.
Information © 2017 General Motors. All rights reserved.


Version 3
Modified Nov. 18, 2016 - Revised the Cause section.
April 6, 2017 - Added models and Revised the Condition, Cause and Correction sections.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

© 2017 General Motors. All rights reserved.
 

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Drive Support Assembly Rattle

Thanks to John for finding the following:
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Discussion Starter #8
Additional information, source being a GM Internal TSB, on A8 transmission harsh shifting/delayed garage shifting engagements on our Corvette automatic transmission, option M5U: This supplements, was issued after, the above information provided in May by Kawika.

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8C466F0E-C5CD-434D-8B4F-8B5054DF74A1.jpeg



Here is the original document: Diagnostic Tips for Harsh Shifting Transmission Conditions
 

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Discussion Starter #9 (Edited)
Have a 2014-16 C7 convertible with a cracking or snapping noise while driving? TSB: 17-28-278: “Convertible Top Creak Or Snap Noise While Driving” addresses a very simple repair by your Technician, basically installing upsized screws to replace those that has stripped out.

Here’s a picture of the three screws that will be one-by-one, replaced with these larger screws. This will be done on each side of the main front headliner bow (total of six screws) 945E0292-81BC-42CA-90B4-7F20110741F1.gif

And since does not apply to 2017 nor 2018 convertibles, my guess we have just learned of one more model change that GM surreptiously did as part of their ongoing product improvement programs.

Thanks to the Rob L @Corvette Action Center for pointing this out.
 

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Thanks to TNSQUIRE Vehicles Affected: Approximately 490 model-year 2019 Chevrolet Corvette ZR1 sports cars

The Problem: Hard braking or acceleration may cause the sensing diagnostic module to enter a fault state
. As a result, the diagnostic module will not provide crash sensing or deploy the necessary airbags in the event of a crash, increasing the risk of injury.

The Fix: Dealers will reprogram the sensing diagnostic module with updated software for free.

What Owners Should Do: Chevrolet manufacturer GM did not immediately announce an owner-notification schedule. Owners can call the automaker at 800-222-1020, the National Highway Traffic Safety Administration's vehicle-safety hotline at 888-327-4236 or visit NHTSA's website to check their vehicle identification number and learn more.
 

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Z8’s transmission shudder: new fix (Dec 2018)

Thanks for elegant for this post content:

GM yesterday came out with an additional/separate fix for the Z8’s transmission shudder, one different from 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.
Quote 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
 
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