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Thread: A question on a guys 2015 c7 A8...

  1. #1
    Join Date
    Jul 2008
    Northern NJ

    Default A question on a guys 2015 c7 A8...

    So today for the second time since I got the car this happens again. Car has 650 miles on it is all. While driving through a strip mall at slow speed in touring mode I come up to a stop light slowing to a stop, then Bang Bang I hear two loud clunks from the tranny and a severe forward jerk that felt like I had just been rear ended this is how it down shifted into first! :ack: Is this NORMAL for this transmission? Like I said only the second time this has happened, but for me its two times to many.[

  2. #2
    Join Date
    Jul 2008
    Northern NJ


    Is this the correct ?

    so OK folks there is a TSB on this and read the last paragraph as well.

    Service Bulletin
    GM Bulletin No.:

    December 2014

    Service Bulletin
    GM Bulletin No.:

    December 2014

    Service Bulletin

    GM Bulletin No.:



    December 2014


    SUBJECT: Service Update for Inventory Vehicles Only

    8-speed Transmission Harsh Shift

    Expires December 31, 2015

    MODELS: 2015 Cadillac Escalade, Escalade ESV

    2015 Chevrolet Corvette, Silverado Double Cab and Crew Cab

    2015 GMC Sierra Double Cab and Crew Cab, Yukon, Yukon XL

    Equipped with 8-speed Automatic Transmission (M5U)

    This service update involves vehicles in dealer inventory only and will expire December 31,



    On certain 2015 model year Cadillac Escalade, Cadillac Escalade ESV, Chevrolet Corvette,

    Chevrolet Silverado Double Cab and Crew Cab, GMC Sierra Double Cab and Crew Cab, GMC

    Yukon and GMC Yukon XL vehicles equipped with 8-speed automatic transmission (M5U), the

    customer may complain about harsh shifting. This can occur if the vehicle experienced multiple

    transmission reprogramming events during manufacturing, causing the calibration to over-adjust

    the shift parameters. This bulletin provides a service adaptive learn procedure that should be run

    to reset the calibration to the baseline parameters.

    This service procedure should be completed on involved vehicles currently in dealership

    inventory as soon as possible but no later than December 31, 2015, at which time this

    bulletin will expire.


    All involved vehicles are identified by VIN in the Global Warranty Management System –

    Investigate Vehicle History Application. Dealership technicians should always check this site to

    confirm vehicle involvement prior to beginning any required inspections and/or repairs. It is

    important to routinely use this tool to verify eligibility because not all similar vehicles may be

    involved regardless of description or option content.

    Additionally, a list of involved vehicles currently in dealer inventory is available on the “Service

    Update Bulletin Information” link under the “Service” tab in GM GlobalConnect (US) or attached

    to the GlobalConnect message (Canada) used to release this bulletin. Customer vehicles that

    return for service, for any reason, and are still covered under the vehicle's base warranty should

    also be checked for vehicle eligibility.

    Page 2 December 2014 Bulletin No.: 14876


    No parts are required.


    Note: Ensure the most recent GDS2 update is installed BEFORE performing the procedure.

    Note: If the transmission fluid temperature is not between 75°C (167°F) and 85°C (185°F) the scan tool will not allow you to perform the service fast learn procedure.

    1. Drive vehicle to warm transmission fluid to a temperature range between 75°C (167°F) and 85°C (185°F).

    2. Connect the MDI to the vehicle.

    3. Access GDS2 and navigate to the Transmission Adaptive Values Learn screen using the following GDS2 navigation path: Diagnostics>Global Vehicle Selection>Module Diagnostics>Transmission Controls>Configuration/Reset Functions>Transmission Adaptive Values Learn.

    Note: After the Transmission Adaptive Value Learn procedure is performed, the ignition must be shut off for at least two minutes to ensure the transmission control module shuts down completely before the vehicle is driven. This reboot of the transmission control module is needed before the transmission control module will operate under the new learned values.

    4. Follow Transmission Adaptive Values Learn on-screen instructions. Refer to Transmission Service Fast Learn Procedure in SI if required.

    5. Remove MDI from the vehicle.

    6. Verify transmission shifts into ‘R’ Reverse and ‘D’ Drive.


    Submit a transaction using the table below. All transactions should be submitted as a ZFAT transaction type, unless noted otherwise.

    Labor Code


    Labor Time

    Net Item


    Perform Transmission Adaptive Values Learn Procedure



    * The amount identified in “Net Item” should represent the actual sum total of the current GMCCA Dealer net price for fuel needed to perform the required repairs, not to exceed $1.50 USD, $2.40 CAD, plus applicable Mark-Up or Landed Cost (for Export).


    Whenever a vehicle subject to this service update enters your vehicle inventory, or is in your facility for service in the future, and the vehicle is still covered under the New Vehicle Limited Warranty, you must take the steps necessary to be sure the service update correction has been made before selling or releasing the vehicle.

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