C7 General Discussion General C7 Corvette Discussion not covered in Tech
Sponsored by:
Sponsored by:

A8 Transmission failure tracking

 
Old 02-06-2019, 04:45 PM
  #961  
MidLife+
CF Member
 
MidLife+'s Avatar
 
Member Since: Jun 2018
Posts: 63
Thanks: 0
Thanked 8 Times in 7 Posts
Default

Originally Posted by azcanuk View Post
Curious, is your car still in the B2B warranty time frame? So less than 3 years/36K..
Yes it is, but the service manager said it would be covered under the 5/60 powertrain warranty.
MidLife+ is offline  
Old 02-07-2019, 09:17 PM
  #962  
us3rname
Junior Member
 
Member Since: Aug 2018
Posts: 34
Thanks: 0
Thanked 3 Times in 3 Posts
Default

has anyone tried zeroing their slip tabled? apparently its getting good result from the people on the camaro boards.
us3rname is offline  
Old 02-08-2019, 05:53 AM
  #963  
plake
Junior Member
 
Member Since: Apr 2018
Posts: 37
Thanked 6 Times in 4 Posts
Default

What are you saying?
plake is offline  
The Following User Says Thank You to plake For This Useful Post:
hanks10GS (03-02-2019)
Old 02-08-2019, 06:37 AM
  #964  
us3rname
Junior Member
 
Member Since: Aug 2018
Posts: 34
Thanks: 0
Thanked 3 Times in 3 Posts
Default

Originally Posted by plake View Post
What are you saying?
This is the first post from a thread on camaro6 titled TCC Shudder/ tuning solutions

"had the shudder start on my car last spring (MY16). I had the flush procedure done and for about 4 months it was resolved. Unfortunately the shudder has returned.

I noticed that if I command the TC to lockup manually (via HP Tuners) it goes to maximum pressure and it will not shudder at all. As of the most recent beta HP Tuners has added some additional TCC tables. I began doing some testing and for a few days now I have not had the shudder occur at all.

There are allowable slip tables per each gear relative to engine torque output. At low torque output GM allows up to 10 RPM of slip. This results in minimal pressure on the TCC apply. This is the design intent but because of whether it is a fluid friction modifier issue or a clutch material issue on the TC it allows the shudder to be felt.

I changed the table to allow 0 slip in 7th and 8th gear. This resulted in increased line pressure and the shudder does not occur. There is also a table that affects ramp rate of pressure based on slip but I did not need to touch that table.

I'm not saying don't go to the dealer and let them flush/replace the TC per the TSB but if you don't want to go that route it appears it can be mitigated via the TCM calibration.

I thought I'd share for the benefit of the community.

Tim"
us3rname is offline  
The Following User Says Thank You to us3rname For This Useful Post:
Ron_Attleboro_MA (02-11-2019)
Old 02-08-2019, 06:13 PM
  #965  
Gearhead Jim
CF Senior Member
Support Corvetteforum!
 
Gearhead Jim's Avatar
 
Member Since: Sep 2000
Location: Chicago area
Posts: 20,823
Thanked 649 Times in 453 Posts
St. Jude Donor '13
Default

If GM finds out you've messed with the TCM tune, kiss the powertrain warranty good by.
And if there's anything on the car I really want to be covered by warranty, the A8 is number 1.
They probably wouldn't even do the new super flush procedure in the January bulletin, unless you're willing to pay ($400+?) for it.

It's well known that before approving major (expensive) work on an engine, GM requires the dealer to send them a readout of the tune history, they're very good at uncovering even "hidden" tunes. Whether they are doing that on transmissions, or will in the future, I don't know. But I don't want to be the test case.
Gearhead Jim is offline  
Old 02-08-2019, 06:18 PM
  #966  
us3rname
Junior Member
 
Member Since: Aug 2018
Posts: 34
Thanks: 0
Thanked 3 Times in 3 Posts
Default

Originally Posted by Gearhead Jim View Post
If GM finds out you've messed with the TCM tune, kiss the powertrain warranty good by.
And if there's anything on the car I really want to be covered by warranty, the A8 is number 1.
They probably wouldn't even do the new super flush procedure in the January bulletin, unless you're willing to pay ($400+?) for it.

It's well known that before approving major (expensive) work on an engine, GM requires the dealer to send them a readout of the tune history, they're very good at uncovering even "hidden" tunes. Whether they are doing that on transmissions, or will in the future, I don't know. But I don't want to be the test case.
Thats a given, however my powertrain warranty went away with the addition of a supercharger. But you gotta pay to play and if tuning the tcm or paying 400+ for a flush corrects a problem ill shell out for it.
us3rname is offline  
Old 02-08-2019, 07:04 PM
  #967  
ricmalaz
CF Member
 
ricmalaz's Avatar
 
Member Since: Mar 2018
Posts: 51
Thanked 11 Times in 7 Posts
Default

Originally Posted by us3rname View Post
Thats a given, however my powertrain warranty went away with the addition of a supercharger. But you gotta pay to play and if tuning the tcm or paying 400+ for a flush corrects a problem ill shell out for it.
My local dealer quoted me $870 for the new triple flush. I will probably just do it myself if I decide it needs to be done.
ricmalaz is offline  
Old 02-08-2019, 07:11 PM
  #968  
us3rname
Junior Member
 
Member Since: Aug 2018
Posts: 34
Thanks: 0
Thanked 3 Times in 3 Posts
Default

Originally Posted by ricmalaz View Post
My local dealer quoted me $870 for the new triple flush. I will probably just do it myself if I decide it needs to be done.
yep mine quoted about the same. He did also mention that he was going to talk to the director as he doesn't think that the addition of the supercharger will void the trans warranty. Ill be amazed if that gets approved. but if not I'll likely change it out with some of the stuff from weapon x myself.
us3rname is offline  
Old 02-08-2019, 08:09 PM
  #969  
ricmalaz
CF Member
 
ricmalaz's Avatar
 
Member Since: Mar 2018
Posts: 51
Thanked 11 Times in 7 Posts
Default

Originally Posted by us3rname View Post
yep mine quoted about the same. He did also mention that he was going to talk to the director as he doesn't think that the addition of the supercharger will void the trans warranty. Ill be amazed if that gets approved. but if not I'll likely change it out with some of the stuff from weapon x myself.
Mine said isn't the supercharger per se, but rather just the programming to the ECM if you get a tune.
ricmalaz is offline  
Old 02-08-2019, 10:21 PM
  #970  
NSC5
CF Senior Member
Support Corvetteforum!
 
NSC5's Avatar
 
Member Since: Aug 2012
Posts: 3,896
Thanked 1,019 Times in 691 Posts
Default

For those of you doing this on your own dime, I would hold off on the triple flush until this latest "fix" has been tested for a few thousand miles by those who have had it done under warranty. The claim was that the lower viscosity of the the prior recommended Mobil fluid would cure the shudder and now the current story is the hygroscopic tendencies of the low viscosity Mobil used as fluid fill #2 is responsible for exactly the same symptoms that was blamed on the viscosity of the original "HP" type fluid used when the 8L90 was introduced. I suspect when shudder reappears with the current magic fluid, the phase of the moon will be identified as the culprit.
NSC5 is offline  
The Following 2 Users Say Thank You to NSC5 For This Useful Post:
Ron_Attleboro_MA (02-11-2019), speed4tu (02-11-2019)
Old 02-08-2019, 11:32 PM
  #971  
KCV
CF Senior Member
 
KCV's Avatar
 
Member Since: Feb 2018
Location: Texas
Posts: 382
Thanked 163 Times in 83 Posts
Default

Originally Posted by NSC5 View Post
For those of you doing this on your own dime, I would hold off on the triple flush until this latest "fix" has been tested for a few thousand miles by those who have had it done under warranty. The claim was that the lower viscosity of the the prior recommended Mobil fluid would cure the shudder and now the current story is the hygroscopic tendencies of the low viscosity Mobil used as fluid fill #2 is responsible for exactly the same symptoms that was blamed on the viscosity of the original "HP" type fluid used when the 8L90 was introduced. I suspect when shudder reappears with the current magic fluid, the phase of the moon will be identified as the culprit.
I think you may be on to something there.
KCV is online now  
Old 02-08-2019, 11:36 PM
  #972  
Makitso
CF Senior Member
 
Makitso's Avatar
 
Member Since: May 2015
Location: layton Utah
Posts: 213
Thanked 90 Times in 53 Posts
Default

I have to wonder if the trans fluid not reaching a normal operating temperature and "cooking" out the
absorbed moisture is a contributing factor in this ongoing issue. This time of year my trans barely reaches
100*F after an hour of driving and even in 100*F+ summer temperatures with spirited driving 135*F is
the most I have seen. From searching I have found a recommended minimum to be around 185*f, but I
don't see that happening for a street driven A8. I have also read that some A8's in other vehicles have a
thermostatically controlled valve that closes off the cooling loop until a minimum temp is reached. Why
wasn't this included on the C7 given its dual cooler system.
Makitso is offline  
Old 02-09-2019, 06:18 AM
  #973  
MA ZO6
CF Senior Member
 
MA ZO6's Avatar
 
Member Since: Apr 2004
Location: Sarasota FL
Posts: 931
Thanked 50 Times in 22 Posts
St. Jude Donor '13
Default

I found this article (see attached) on the GM Techlink website. It explains that the old fluid would absorb moisture over time but the new fluid should not.

John
Attached Images
File Type: pdf
GM Techlink Shudder Article.pdf (281.4 KB, 65 views)
MA ZO6 is offline  
The Following 7 Users Say Thank You to MA ZO6 For This Useful Post:
hanks10GS (03-02-2019), Heidemarie (02-09-2019), jimtreber (02-13-2019), joemessman (02-09-2019), KCV (02-09-2019), plake (02-09-2019), Ron_Attleboro_MA (02-11-2019)
Old 02-09-2019, 05:13 PM
  #974  
NSC5
CF Senior Member
Support Corvetteforum!
 
NSC5's Avatar
 
Member Since: Aug 2012
Posts: 3,896
Thanked 1,019 Times in 691 Posts
Default

I find it interesting that "normal" Mobil 1 synthetic ATF along with numerous other transmission fluids that meet the specs of various GM (and other manufacturer) transmissions don't have a shudder issue EXCEPT when used in the 8L45/8L90 applications. Transmission fluid additive packs have made common ATF somewhat hygroscopic since the late 1970s so it isn't like the original Dexron HP (the original fluid for the 8L90) suddenly brought about a hygroscopic issue to ATF.

So we started with the original "special" spec beyond then current Dex VI which was named Dexron HP for use in the 8L series transmissions. Next we get Mobil 1 "black label" low viscosity synthetic to replace the original HP spec fluid. Now that has been replaced by the "blue label" version that is more resistant to hygroscopic induced shudder.

Unless forced to in court, GM isn't likely to divulge why the 8L series is so problematic with respect to torque converter lockup clutch shudder nor how these new fluid specs which have changed significantly from the original specs around which the 8L90 was designed will impact future operation including longevity.
NSC5 is offline  
The Following User Says Thank You to NSC5 For This Useful Post:
1950silverstreak (02-09-2019)
Old 02-11-2019, 03:41 PM
  #975  
Ron_Attleboro_MA
CF Member
 
Ron_Attleboro_MA's Avatar
 
Member Since: Aug 2017
Posts: 55
Thanked 13 Times in 11 Posts
Default Thanks, Range - AFM Disabler

Originally Posted by ddelallata View Post
I'll update it soon. My 2017 started shuddering at 3200 miles.
Triple flush took care of the problem, but I'm keeping the Range unit plugged in for now.

Update done. Thanks
Have you had any problems after adding the Range - Disabler? Any codes? Did you ever need to get the disabler upgraded?
Someone on StringRayForum had a problem:
https://www.stingrayforums.com/forum...-problems.html

Has anyone done research that disabling does not harm?
Ron_Attleboro_MA is offline  
Old 02-11-2019, 03:45 PM
  #976  
Ron_Attleboro_MA
CF Member
 
Ron_Attleboro_MA's Avatar
 
Member Since: Aug 2017
Posts: 55
Thanked 13 Times in 11 Posts
Default

Can you point me to more info on the 'evacuation method'?
I like this, maybe do it myself once a month for six months. Sort of drive & purge method.
Ron_Attleboro_MA is offline  
Old 02-11-2019, 08:25 PM
  #977  
Rick John
Junior Member
 
Member Since: Feb 2019
Posts: 1
Thanks: 0
Thanked 0 Times in 0 Posts
Default I just picked up a 2015 corvette a8 transmission

Originally Posted by ddelallata View Post
I'll update it soon. My 2017 started shuddering at 3200 miles.
Triple flush took care of the problem, but I'm keeping the Range unit plugged in for now.

Update done. Thanks
I just picked up a 2015 and left the dealer ship and I felt shuttering. Ya think before selling they would fix this problem. I noticed if I put it in the sport mode it drove fine. Now I need to take it back to figure out what this is..
Rick John is offline  
Old 02-12-2019, 07:41 AM
  #978  
MA ZO6
CF Senior Member
 
MA ZO6's Avatar
 
Member Since: Apr 2004
Location: Sarasota FL
Posts: 931
Thanked 50 Times in 22 Posts
St. Jude Donor '13
Default

A update on my car, I had the NEW flush done a few weeks ago and the car still runs fine, the shudder is gone. Hopefully it stays that way, time will tell.

John
MA ZO6 is offline  
The Following User Says Thank You to MA ZO6 For This Useful Post:
joemessman (02-12-2019)
Old 02-12-2019, 08:28 PM
  #979  
joemessman
CF Senior Member
 
joemessman's Avatar
 
Member Since: Nov 2015
Location: Lake Havasu City Arizona
Posts: 4,391
Thanked 1,392 Times in 934 Posts
Default

Originally Posted by Rick John View Post
I just picked up a 2015 and left the dealer ship and I felt shuttering. Ya think before selling they would fix this problem. I noticed if I put it in the sport mode it drove fine. Now I need to take it back to figure out what this is..
Why didn't you drive it before you bought it?
joemessman is offline  
Old 02-12-2019, 10:07 PM
  #980  
Roastum1
CF Member
 
Roastum1's Avatar
 
Member Since: Sep 2018
Posts: 79
Thanks: 0
Thanked 11 Times in 9 Posts
Default

Did the 15s have the 6speed or 8speed?
Roastum1 is offline  

Thread Tools
Search this Thread
Quick Reply: A8 Transmission failure tracking


Sponsored Ads
Vendor Directory

Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: