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[ANSWERED] C7 A8 Transmission and Torque Convertor Questions

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[ANSWERED] C7 A8 Transmission and Torque Convertor Questions

Old 03-08-2016, 09:52 AM
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jvp
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Default [ANSWERED] C7 A8 Transmission and Torque Convertor Questions

Original question is here.

Maxie2U asked:
1) A8 Transmission: a) what changes and/or redesigns were made to the newly released A8 transmission (new part#24274892)? b) what is the date Bowling Green began to use the new transmission in production?

2) Torque Converter: why was it necessary to release a redesigned torque converter this year (as referenced in document id: 4373638)? How does this affect owners that have the old torque converters?
Tadge answered:
Before answering the questions directly, I will point out that the new 8-speed transmission has been very reliable. Our data indicate that the vast majority of owners have experienced no issues and, in fact, are enjoying the best balance of performance and efficiency we have ever offered. Although we strive for perfection, no person, company or machine is perfect so we, like all manufacturers (And not just autos…. How often is your cell phone upgraded?), practice aggressive continuous improvement. We did on our 4-speed trans years ago and likewise when we introduced the 6-speed more recently. We are doing it on the 8-speed currently. As I have answered in other questions on the Forum, we always try for backwards compatibility, but can’t restrict progress by making that a mandate.

Question 1} Part number 24274892 was released for use with the heavy duty cooling option which comes with Z51 and Z06 automatics (and will be for the just-introduced 2017 Grand Sport}. The transmission hardware itself is the same as the prior part number (24273222). The difference is that it contains more oil in it to compensate for the extra coolers and cooler line volume added to the vehicle. The 24273222 trans assembly remains released for use with the standard LT1 cooling package. The break-point for the new part number in Bowling Green was May of 2015.

Question 2) The service bulletin you cite says to perform a double oil flush if you suspect that the trans is exhibiting TCC (torque converter clutch) shudder. That procedure has been successful in fixing a few vehicles. This has primarily been a truck issue, pretty rare on Corvette. The bulletin is now being updated to have the converters replaced instead of just a flush since it has not been 100% effective. So the bottom line is if customers are not having any problems, they shouldn’t worry about that document. In the rare instance where there is truly a torque converter problem, there is new design that should help. That hardware became available in December of 2015. I want to make sure customers with the prior design understand that if there is an issue, symptoms will appear early in the car’s life. The design change was not to improve the performance of the car or it’s durability over the long term. Bottom line is that if customers are not having a problem now, it is very unlikely to occur later.

Last edited by jvp; 03-08-2016 at 01:46 PM. Reason: cut'n'paste error
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Old 03-08-2016, 11:56 AM
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Good to hear issues with the A8 are very rare.
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Old 03-08-2016, 01:24 PM
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So...

What exact changes were made to the TC?

Bah.
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Old 03-08-2016, 04:36 PM
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BTW: if there's any doubt left in anyone's mind that Tadge enjoys this interaction - The answer was sent to me today while he's on vacation in some place fairly nice (from what I've been told) and warm. And it was also worked on while he was on business travel to and from Geneva for the GS announcement last week.
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Old 03-08-2016, 08:32 PM
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(Question 2) (The service bulletin you cite says to perform a double oil flush if you suspect that the trans is exhibiting TCC (torque converter clutch) shudder. That procedure has been successful in fixing a few vehicles. This has primarily been a truck issue, pretty rare on Corvette. The bulletin is now being updated to have the converters replaced instead of just a flush since it has not been 100% effective. So the bottom line is if customers are not having any problems, they shouldn’t worry about that document. In the rare instance where there is truly a torque converter problem, there is new design that should help. That hardware became available in December of 2015. I want to make sure customers with the prior design understand that if there is an issue, symptoms will appear early in the car’s life. The design change was not to improve the performance of the car or it’s durability over the long term. Bottom line is that if customers are not having a problem now, it is very unlikely to occur later.)


This statement says that there is a problem that flushing does not fix and the tc's are being replaced. Then at the end the statement says it is not to improve performance or durability. This appears to be a contradiction because shudder and shake and hard shifts are definitely a performance issue.

Last edited by red 1; 03-08-2016 at 08:36 PM.
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Old 03-08-2016, 10:12 PM
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Originally Posted by red 1 View Post

This statement says that there is a problem that flushing does not fix and the tc's are being replaced. Then at the end the statement says it is not to improve performance or durability. This appears to be a contradiction because shudder and shake and hard shifts are definitely a performance issue.
I believe Tadge is saying there is no performance improvement compared to a normally operating older version. As in, no difference in shift quality, speed, firmness, etc. Of course there's a "performance improvement" compared to one not functioning properly.
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Old 03-09-2016, 01:45 AM
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Default tcc shudder

The problem is isolated to the convertor clutch only. It could be anything that cause it. The bulletin implies that it is a characteristic of the wear of the clutch. If the clutch develops a shudder as it wears that the tcc solenoid can not compensate for , then the convertor requires replacement.

Last edited by damnlucky08; 03-09-2016 at 01:46 AM.
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Old 03-09-2016, 09:05 AM
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Would anyone dare to speculate as to when the dealerships will be aware of this information?

I daily drive my Corvette and am quite anxious to get this problem resolved.
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Old 03-09-2016, 03:43 PM
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Question 1} Part number 24274892 was released for use with the heavy duty cooling option which comes with Z51 and Z06 automatics (and will be for the just-introduced 2017 Grand Sport}. The transmission hardware itself is the same as the prior part number (24273222). The difference is that it contains more oil in it to compensate for the extra coolers and cooler line volume added to the vehicle. The 24273222 trans assembly remains released for use with the standard LT1 cooling package. The break-point for the new part number in Bowling Green was May of 2015.

I take "standard LT1 cooling package" to mean non-Z51 & non-Z06 - in other words, the wet sump motor.

So, in essence, the new part number ...4892 is the same tranny that goes with wet & dry sump motors, but with more (oil) cooling capacity if a dry sump motor?

If you have a wet sump motor, the May 2015 date is meaningless - wet sumps continued to get the same tranny (part number ...3222) whether produced before or after May 2015.

Did I interpret this correctly?
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Old 03-09-2016, 09:25 PM
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The Torque Converter is being replaced on my A8 after Sebring Corvette Corral. All it took was for the service manager to verify problem after sitting two hours. Has to be cold to occur on my car. Thanks for stepping up GM.
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Old 03-10-2016, 12:53 AM
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Does anyone have a copy of the bulletin: 4373638? I'm curious to see what it says. I'm purchasing a car that was built in December so I'm slightly nervous about this. Especially since my local dealer here said they've never heard of this.

Thanks
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Old 03-10-2016, 11:26 AM
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Originally Posted by roSSco View Post
Would anyone dare to speculate as to when the dealerships will be aware of this information?

I daily drive my Corvette and am quite anxious to get this problem resolved.
I had the harsh 1-2 shift issue and both of the larger dealerships I called here in Florida were aware of the problem and had done TCC replacements.

I took my car in a month ago, TCC replaced, problem fixed
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Old 03-12-2016, 09:44 PM
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So my Z51 was built December 6th. Do I have the new or old TC?
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Old 03-14-2016, 11:58 PM
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Originally Posted by Gymbow View Post
So my Z51 was built December 6th. Do I have the new or old TC?
Based on Tadge's response I say you have the new t/c
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Old 03-15-2016, 12:01 AM
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I really wish I had added this to Question#2 to Tadge.

Does switching out of V8 mode to V4 mode have anything to do with TCC (torque converter clutch) shudder?

Last edited by Maxie2U; 03-15-2016 at 12:03 AM.
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Old 03-16-2016, 01:38 PM
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Originally Posted by 767guy View Post
I had the harsh 1-2 shift issue and both of the larger dealerships I called here in Florida were aware of the problem and had done TCC replacements.

I took my car in a month ago, TCC replaced, problem fixed
Please reply with the name and location of the dealer that did the repair. I am getting the "we never heard of this" response from my dealer in Texas. I would like your dealer info so I can have my dealer contact your dealer and get educated on the first to second abrupt shift issue. Appreciate any help you can provide.
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Old 03-16-2016, 02:43 PM
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Originally Posted by BrittHealey View Post
Please reply with the name and location of the dealer that did the repair. I am getting the "we never heard of this" response from my dealer in Texas. I would like your dealer info so I can have my dealer contact your dealer and get educated on the first to second abrupt shift issue. Appreciate any help you can provide.
Try Sunset Chevrolet in Sarasota FL, shop foreman Bob Wiseman 941 366 7800. First effort will be to reprogram TCM. If that does not work most likely converter part #24279495 may need to be replaced with same part # but now version 4.115 I recall the new version comes from a supplier in Detroit.

Also try Stingray Corvette near Plant city FL.

The harsh 1-2 shift after extended sitting ( overnight) is caused by fluid bleeding back from some TC's . After a couple of shifts first drive of the day the TC is now pressurized so shifts are now smooth.

Hope that helps.......good luck and post results when fixed ...tks
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Old 03-17-2016, 02:57 AM
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Originally Posted by Gymbow View Post
So my Z51 was built December 6th. Do I have the new or old TC?
"That hardware became available in December of 2015. I want to make sure customers with the prior design understand that if there is an issue, symptoms will appear early in the car’s life. The design change was not to improve the performance of the car or it’s durability over the long term. Bottom line is that if customers are not having a problem now, it is very unlikely to occur later."

Last edited by joemessman; 03-17-2016 at 03:19 AM.
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Old 03-17-2016, 03:11 AM
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Originally Posted by DMGroh View Post
Question 1} Part number 24274892 was released for use with the heavy duty cooling option which comes with Z51 and Z06 automatics (and will be for the just-introduced 2017 Grand Sport}. The transmission hardware itself is the same as the prior part number (24273222). The difference is that it contains more oil in it to compensate for the extra coolers and cooler line volume added to the vehicle. The 24273222 trans assembly remains released for use with the standard LT1 cooling package. The break-point for the new part number in Bowling Green was May of 2015.

I take "standard LT1 cooling package" to mean non-Z51 & non-Z06 - in other words, the wet sump motor. Z51 and z06 A8s require more oil.
So, in essence, the new part number ...4892 is the same tranny that goes with wet & dry sump motors, but with more (oil) cooling capacity if a dry sump motor?

If you have a wet sump motor, the May 2015 date is meaningless - wet sumps continued to get the same tranny (part number ...3222) whether produced before or after May 2015.

Did I interpret this correctly?
Yes. It is only an issue with dry sump motors.

Last edited by joemessman; 03-17-2016 at 03:16 AM.
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Old 03-19-2016, 04:32 PM
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Originally Posted by Maxie2U View Post
I really wish I had added this to Question#2 to Tadge.

Does switching out of V8 mode to V4 mode have anything to do with TCC (torque converter clutch) shudder?
No. I had the service manager experience the problem while watching the V4 and V8 mode, It has nothing to do with it. Lunging when cold was evident very early on the car. The shudder at constant speed problem did not appear until 10K miles. Everything resolved when TC and Trans was replaced. Now service mgr tells me the current repair is replacement of TC only.
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