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Old 01-03-2019, 09:40 PM   #1
gmw0181
 
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New Info on A8 shudder 12/2018

Found this online today.


https://www.midenginecorvetteforum.c...ission-shudder




New Fix A8 Transmission Shudder

12-13-2018, 02:30 PM


GM has come out with a additional/separate fix for the Z8’s transmission shudder, one different front 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.

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



















Document : https://dealer.autopartners.net/portal/uscontent/headlines/Pages/GCUS-9-7040.aspx 8 Speed Torque Converter Shudder – New Service Procedure and New Mobil 1 Synthetic LV ATF HP Fluid Regional Rollout
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Old 01-03-2019, 09:50 PM   #2
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So this will address that annoying shudder when it switches to 4 cylinders?


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Old 01-03-2019, 10:43 PM   #3
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This is great info! Thanks for sharing.

Any idea if those of us who will be just past 36K miles (when it's finally widely available) will qualify for the fix under warranty? Would this issue fall under the powertrain warranty, which is longer?
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Old 01-03-2019, 10:51 PM   #4
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Band-aid fix till cars are out of warranty.
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Old 01-04-2019, 12:09 AM   #5
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Quote:
Originally Posted by KingLT1 View Post
Band-aid fix till cars are out of warranty.
This....
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Old 01-04-2019, 06:00 AM   #6
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I won't say this won't fix the issue. I won't say this won't hide the problem until they are no longer liable for the issue. Except that's exactly what I'm saying.
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Old 01-04-2019, 07:11 AM   #7
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Quote:
Originally Posted by KingLT1 View Post
Band-aid fix till cars are out of warranty.

If an issue is addressed during the warranty, aren't future repairs on the same part covered regardless of warranty coverage status?
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Old 01-04-2019, 07:17 AM   #8
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It's a design flaw somewhere. I suspect it's a tolerance issue or something in the manufacturing process regarding the orifices and size/restriction causing the shudder in the transmission. I think this since not all transmissions experience it. They are trying different fluids to see which ones will lessen or eliminate it. It's got to be the something like that as when mine did the shudder it only did it when the car reached operating temperature or the fluid was hot and thin. The hotter it was the more shudder. I knew it was not going to be addressed- and even if only 10% of vehicles have it that still a lot of vehicles between Camaros, Silverados, Colorados and Vettes.

I have to wonder how this transmission will be once out of warranty- how durable, will the shudder be worse than ever, etc.
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Old 01-04-2019, 07:28 AM   #9
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Old 01-04-2019, 09:33 AM   #10
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Yeah this has been discussed under the transmission section on the forum, this new "fix" is nothing more than a Band-Aid. The TC is most likely damaged on most of these A8's, so the TC will need to be replaced first and foremost. This new fluid flush and fill will be nothing more than a temporary "fix". Hopefully this and my Range will get me by for the next 2 or 3 years when I am ready to get rid of my 6th gen. We shall see.
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Old 01-04-2019, 03:50 PM   #11
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Mine added to the list of A8's with an issue just before xmas.
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Old 01-04-2019, 05:13 PM   #12
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Quote:
Originally Posted by JT58 View Post
It's a design flaw somewhere. I suspect it's a tolerance issue or something in the manufacturing process regarding the orifices and size/restriction causing the shudder in the transmission. I think this since not all transmissions experience it. They are trying different fluids to see which ones will lessen or eliminate it. It's got to be the something like that as when mine did the shudder it only did it when the car reached operating temperature or the fluid was hot and thin. The hotter it was the more shudder. I knew it was not going to be addressed- and even if only 10% of vehicles have it that still a lot of vehicles between Camaros, Silverados, Colorados and Vettes.

I have to wonder how this transmission will be once out of warranty- how durable, will the shudder be worse than ever, etc.
The issue is when the transmission is locked up and cruising at a steady speed, the front pump is running at a low pressure. Because of this the TCC clutches are not getting enough pressure applied when transitioning from V4 to V8 and you get the shudder. The 6l80 in the L99 equipped 5th gens didn't have this issue because the transition from v4 to v8 was much more abrupt due to the tuning. GM wanted the 6th gen to shift and transition from v4 to v8 mode seamlessly and this is the result.

I can say this...the only thing so far that has proven to be a 100% fix with no return issue is replacing the converter with a Aftermarket unit from FTI or Circle D and a tune.

Every other solution has had some issues come back...trans flush, trans flush & stock replacement converter...etc. Some folks including myself were able to fix the issue with tuning alone before there was a problem, others have not been as fortunate.

My issue is, if all of the vehicles out there with shudder that keep getting driven that way has to be causing premature wear on the clutches. Then the transmission valve body and what not is also pumping that clutch material through the system. Sure the new fluid might be a fix on a transmission and converter that has not experienced the issue, but I am not confident it's a real fix for a pre-existing problem because the damage is already done.
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Old 01-04-2019, 05:55 PM   #13
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They can't say it is just a fluid issue when I've had 4 flushes and each time there have been band and clutch material coming out with the fluid each time. Once enough debris is loose in the fluid it eventually starts restricting openings and making itself known that the transmission is eating itself.

The cause of the clutches and bands being eaten -- "unconventional behavior" of the TCC lockup solenoid. When the TCC lockup pulsates (trying to hide the shake of uneven torque throughput of AFM) it causes rapid pressure changes against the active gears clutch and gear. Remember morons in the 90's and 00's doing neutral drops in automatics? Same effect but in short pulses. Even though it is not as violent as a 4k rpm neutral drop, the frequency at which this event occurs (constantly while in AFM), eats away at the 6th/7th/8th gears.

Once fluid is contaminated enough, it affects low gear lockup resistance and cold start performance. This is why initial 1st/Reverse lockup after cold start is greatly delayed (computer detects resistance and increase fluid pressure until lockup occurs). That causes the *thunk* or *clunk* 3 seconds after you put it in gear. The resistance is also the reason for low speed jerking in 1st/2nd upon first drive or while navigating a parking lot.

GM is doing everything they can to avoid disabling AFM/DFM, because it would require them to restate fuel economy of each model and expose them to even greater class action suits and possible EPA fines for those vehicles which would've required consumption taxes but were not collected at the time of new sale due to the previously stated economy numbers. Considering what it cost German automakers, I think GM will do everything they can to avoid a 30 billion write down in a fuel economy or emissions scandal.

The 8L series is a rather compact design. Unlike a ZF unit, there is no adjustment device to tighten fading bands. It's a common corrective action when slipping begins to occur due to liner wear. Band material is the tough but malleable material you may find in fluid. Clutch material is the metal shavings. A good transmission under 50k miles shouldn't have any and only minimal at 100k. Averaging a flush every 8k miles and finding as much contamination as a 100k mile transmission is not a healthy transmission.

Just the concept of a different fluid to correct the issue is flawed. A band is designed to displace and resist fluid to capture a clutch to avoid slipping. The only change in fluid I can think that GM has asked Mobil1 to formulate would be to somehow act like an anti-bonding agent to prevent the band liner material from staying stuck to the internal valving of the transmission and make its' way to the pan where the filter and pickup screens can keep it away from recirculation.

It's like plague building up in the arteries of the transmission because it is getting stuck before it can make it to the organ designed to filter and remove such build up from the circulation.

There is a reason the ZL1 doesn't have a line of 10L90 complaints but the Tahoe RST and 2019 Silverado are already lining up in service departments. AFM and DFM both have the same impact on compact gear assemblies facing high input torque.

This whole thing reminds me of when some car makers tried using compact FWD CVT's on larger 2.0L motors with 200+ torque, longevity and reliability went to sh!t. Leave the AFM/DFM tech for vehicles with less than 200 torque and it will be fine for 100k miles. For everything with more strength than that, doesn't play games and just add gears so the final drive can be taller to provide better fuel economy.
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Old 01-04-2019, 06:00 PM   #14
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Quote:
Originally Posted by KingLT1 View Post
The issue is when the transmission is locked up and cruising at a steady speed, the front pump is running at a low pressure. Because of this the TCC clutches are not getting enough pressure applied when transitioning from V4 to V8 and you get the shudder. The 6l80 in the L99 equipped 5th gens didn't have this issue because the transition from v4 to v8 was much more abrupt due to the tuning. GM wanted the 6th gen to shift and transition from v4 to v8 mode seamlessly and this is the result.
Not exactly correct. GM started pulsing the TCC solenoid in alignment with the deactivated cylinders to mask the natural jittery feeling and pronounced transitions in and out of AFM modes. All the damage is a result of the pulsating lockup of the TCC. A tune alone will actually rid you of the problem if you disable AFM. If there was a way for us to remove the solenoid pulse procedure from the AFM mode of the 8L TCM it would feel just like a L99 5th gen did and we wouldn't be having dirty fluid issues.
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