z51mojo

I have also experienced this problem when idling to a stop and then slightly accelerating. I could have sworn that I had been hit by the car behind me.

I have heard that there is a method to 'reprogram' the transmission to learn a new shift pattern.

Has anyone tried to reprogram their A8 shifting behavior?

Mine is a 2015 Z51 A8.

bapd77

I've had it happen to me also, but it is always after hard acceleration then coming to a stop.

c7v

Yeah same thing here. At first I was a bit concerned but then realized it's only after hard acceleration runs.

bapd77

To the OP, and I mean this genuinely, not trying to be an A$$.....I've seen you have several issues with your car and things you don't seem to like about it. Have you considered trading it in on something you'd be more happy with? I actually believe you have some valid points about the car, especially the tires, but you seem less than happy with your car and it seems maybe you'd be happier if you purchased another car you liked better....

I looked at a CTS-V once and for all the upside and way people drool over them on their forums, it just isn't the car for me. I didn't like it. It's definitely a nice car, but not every car is for every person.

rramjet

My A8 did a super hard downshift while slowing for a light on a crowded freeway off ramp and refused to move forward or backward afterward. 79 miles on the car

Got a new transmission. Trouble free for 2100 miles. I do occasionally notice what I call confused shifting at very slow speeds with slight throttle pressure. I seem to notice it more in hotter temperatures like 90's we have been seeing here in AZ lately.

ArcticC7

No I was parked at a store, I was just making my way out of the mall to the intersection exit, when I started stopping at the stop light it happened. Honestly it felt like the car in back of me ran into me that's how hard the down shift was.

bapd77

Damn, already into the 90s there? Here in OK, we're in the 70s most days. I wish it was 90 here. I love hot weather.

ArcticC7

You were lucky it failed that way. at least you were able to get rid of it early on and didn't have to go to the Dealer a dozen times before they decided to do anything.

Steve_R

In a year of owning it and several thousand miles I've never once had mine in D so I have no idea if it does that or not.

sting15ray

I've had it happen a few times as well, but I've been hesitant to take it to my dealer since I have zero faith in them from past experience

For me it happens when I'm slowing down, like when approaching stopped cars in front of me at a light, but by the time I get there they've started moving so I take my foot off the break, and then it happens, lurch and bang, like you describe. Always low speeds when it happens

Glad to see I'm not alone ...

c7v

I'm not sure to why people are saying that the OP is whining. Personally I love the car and if it smacked upside the head every morning, I would still want to drive every second and wouldnt give a crap. Having the same issurehappen to me as the OP, I can attest to how scary it is, it genuinely feels like you are rear ended by a dump truck while parked on a highway. Its very scary. I'm not sure this counts as whining.

ArcticC7

bapd77

I've experienced it too so I know it can happen and is kinda scary. I don't really think he's a whiner as others do. But, he has numerous threads about stuff he doesn't like about the car and frequently posts negative comments so people are growing tired of his posts/threads and call him a whiner. I just asked why he doesn't consider getting a new car, because it seems to me he is less than completely happy with it. He's answered 3 other people since my question was posed, but he has chose not to answer my question.

thrilled

If you check you will see more on this forum on the subject.Supposely it has to be re-programmed in some cases.
Changing the subject A wee bit.My local chevy dealer just received an orange Z06. M7.
Had to put it in there.

ArcticC7

Join the club if we should even call it that..

c7v

Understood.

ArcticC7

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

Service Bulletin
GM Bulletin No.:
Date:


14876
December 2014



Service Bulletin
GM Bulletin No.:
Date:


14876
December 2014



Service Bulletin

GM Bulletin No.:

Date:

14876

December 2014

SERVICE UPDATE

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,

2015.

PURPOSE

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.

VEHICLES INVOLVED

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

PART INFORMATION

No parts are required.

SERVICE PROCEDURE

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.

WARRANTY TRANSACTION INFORMATION

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

Labor Code

Description

Labor Time

Net Item

9101182

Perform Transmission Adaptive Values Learn Procedure

0.5

*

* 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).

DEALER PROGRAM RESPONSIBILITY

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.

boxster99t

c6chaz

hard shifting 1 to 2nd, 20 miles.

bob44

Happened to me this way also. Was in a parking lot, coming out from dinner, and at the first traffic light, just coming to a stop, had the strong 'lurch' - pressed down hard on brake after being startled.

Car had about 200 miles on it, A8 Z51, in Touring mode. I had read about the phenomenon here on the Forum, so wasn't overly concerned. Glad to see there's a TSB. Will bring that to the dealer at next oil change.