Al Engel

Good morning. Checking out GM TechLink this morning I came across the following article anouncing a "fix" for the Corvette's 8 Speed Auto "Shudder". The article details what "shudder" is, how to test for it, the cause and the prescribed fix. It appears the problem is caused by the OEM trans fluid being "hydroscopic"... that is, having the propensity to absorb moisture. The flush and fluid replacement procedure requires special tools and proceedure, but it should be a covered repair. The tech bulletin follows......

Al Engel "Save the Wave"



TCC Shudder and New Mobil 1 Fluid Exchange

January 31, 2019

A new transmission fluid exchange procedure and a new formula of Mobil 1 Synthetic LV ATF HP transmission fluid have been released to address torque converter clutch (TCC) shudder conditions on 8L45 and 8L90 8-speed automatic transmissions (RPOs M5N, M5T, M5U, M5X) in some 2015-2017 Escalade, Yukon; 2015-2018 Silverado, Sierra; 2015-2019 Corvette; 2016-2018 CT6; 2016-2019 ATS, CTS, Camaro; and 2017-2019 Colorado and Canyon models.

The new fluid exchange procedure requires the use of the DT-45096 TransFlow Cooler Flush Machine and DT-52263 Transmission Fluid Exchange Tool Kit. (Fig. 10) The tool kit began shipping to dealerships at no charge in late January 2019. All GM dealerships should receive the tool kits by the end of March 2019.


Shudder Test

The new service procedure addresses shake and/or shudder conditions during light throttle acceleration between 25 and 80 MPH (40 and 128 KM/H) at a steady speed when the transmission is not shifting gears. To ensure TCC shudder is diagnosed correctly, drive the vehicle on a smooth road with transmission sump temperature between 122°F (50°C) – 158°F (70°C). Constant throttle input on a smooth grade is needed.

A shudder condition may also be a chuggle, surge or vibration condition. Use GDS 2 or the CH-51450 PicoScope to confirm that the concern is TCC shudder and not a tire/wheel vibration or a driveline vibration, for example. A screen print from GDS 2 or the PicoScope showing the TCC shudder event must be attached to the Repair Order hard copy. (Fig. 11)

If TCC shudder is present, a vibration peak will appear within +/- 2 Hz of the frequency listed in Bulletin #18-NA-355. Refer to the bulletin for additional information, including required shudder test conditions for each vehicle being diagnosed as well as the fluid exchange procedures.


Fluid Exchange

The TCC shudder condition is related to moisture content in the transmission fluid. The current fluid tends to be hydroscopic, or absorbs moisture, which increases the chance of TCC shudder. There are three different fluid exchange procedures to follow, depending on vehicle application, so that an acceptable concentration of the new HP fluid is achieved in the transmission.

The new Mobil 1 Synthetic LV ATF HP transmission fluid is now available to U.S. dealerships through your local GM Oil Distributor. The new Mobil 1 Synthetic LV ATF HP transmission fluid is available in quart bottles (GM Part Number 19417577) and, for a limited time, in 55-gallon drums (GM Part Number 19417904) in most locations. Drum production ended in January 2019. The GM part numbers are not on the product.

The Mobil 1 Synthetic LV ATF HP fluid and the required tool kit will be available to all Canadian dealerships by the end of March 2019. GM Part Numbers for 0.946 liter bottles will be provided at that time.

TIP: Mobil 1 Synthetic LV ATF HP transmission fluid is required for all 8-speed transmission repairs regardless of the repair being completed.

Quart bottles, which can be identified by a new blue banner across the front of the bottle (Fig. 12), will be limited to 20 cases/120 quarts per dealer per week during the initial launch of the new product. The new bottles also feature the HP license number J-62120 on the back label.


For a video demonstration of the new fluid exchange procedure, check out the December 2018 Emerging Issues Broadcast, course number 10218.12V, available through the Center of Learning. In Canada, refer to the January 2019 TAC Talk seminar.



– Thanks to Mark Gordon

bjones7131

Moisture in the fluid. I hope this is the fix but time will tell. My car isn't shuddering at present but I run with Range device to keep it out of 4 cylinder mode. Wonder if GM will pay for this fluid change if your car isn't exhibiting the shudder. I would prob. pay for it myself for peace of mind. Thanks for the info.

Mobil 1

My new Grand Sport was just built this week and is shipping. Hopefully it comes with the new fluid.

joemessman

I hope it does to, but how would you know?




Where is the moisture coming from that is contaminating the fluid?

Maxpowers

^^^
Anywhere there is a bit of air, there is moisture. This is the same reason brake fluid needs to be flushed even though its a closed system.

Avanti

Of course, GM wouldn't just replace the wonky fluid (knowing full well it is), but requires formal verification... as apposed to valuing customer good-will by simply changing it for those who complain!

LarryFL

What about all those who think any old vibration is the infamous 'shudder'? If it has a cost, it needs to be rationed for those that need. Too many people getting fluid replaced drives up the wait times for other, and cost to GM ...

I feel bad for all the poor souls had their transmission replaced when, in the end, it was just wonky fluid. I'm sure those cars got put pack together about 95% right.

555ctsv

I had the triple flush tsb done 1/15/19 and paperwork shows they used fluid #19417904, I'm excited to see i did get the latest and greatest fluid

JDMilw

I wonder......... if the fluid was the sole factor in this shudder issue, wouldn’t there be 10s of thousands of shudder reports?

I have not experienced the shudder or any other problem. My car was built 7/17 and has almost 7k miles.

Gearhead Jim

I'm not sure if even GM knows why some cars are developing the shudder and others have not. Since the problem has existed for about 4 years and produced only a series of BandAid fixes, their ability and integrity are open to question.

Hopefully, the latest "Fluid of the Month" fix will be enough.

falcon5619

I remember reading something about humid climates having more reports of the TC shudder due to the additional moisture in the air being absorbed into the fluid quicker.

iclick

This is believable since I live in S. LA and my 2015 C7 exhibited shuddering from Day 1 driving home from the dealer. It was sporadic and uncommon early on but got worse over time and 18 months later was noticeable every time the car was driven. The TC and 3x fluid change was done almost exactly two years ago and the fluid used had the same description (Mobil 1 Synthetic LV ATF HP) but a different part number (19353429) than what's being reported here. The A8 worked without shudder after the work was done but I traded it for a 2017 M7 two weeks later.

Al Engel

Transmissions now are far more complex than the days of 2 speed Powerglides. Slight differences in trans fluid can have significant impact on performance. I'm very surprised water contamination in trans fluid was not identified by GM engineers as an issue durring validation testing. Four years into production, to just now ariving at a conclusion of water contamination --- and then to come up with a trans fluid that tolerates moisture contamination, is 'disapointing'. This should have surfaced during pre production development and testing of the A8 transmission, in my opinion. Time will tell if the engineers got it right now. Future reports from A8 owners on this Forum, who have this "fix" applied, will be very interesting. Fortunately, I stir my on gears (7 speed stick).

Al Engel "Save the Wave"

BigVette427

Typical GM deny, bob and weave - we know the fluid in many of the 8L90's has now been identified as to be inadequate because it can absorb moisture, cause a shudder, and do damage to the transmission, and while we have identified a new fluid that will solve this problem, we're going to wait until your transmission actually incurs damage before we will change the fluid. Seems to me that the fluid would be cheaper than new clutches, TC's, and 8L90 units altogether.

Irks me greatly that someone from the dealership (who didn't plunk down a large sum of money for the privilege of owning one of these expensive vehicles) has to drive the vehicle on public roads with diagnostic equipment before GM's cheap-@sses will pay for the proper fluid. I would expect (but would not bet on it,) that GM issues an extended warranty for all vehicles outfitted with these transmissions just for this particular issue.

Formula52

How much would it cost to change to the new fluid if not covered by warranty?

Thanks....

MikeERWNC

I did my second flush at 60K miles for under 150.00.
ATF Filter and 10qts of fluid.
Summit has the best internet price on fluid. My local dealer sold me ten quarts for much less.
It takes about two hours.

Make sure the car is level when you do it.
Get a Quart bottle pump to get the fluid back into the pan.
Measure how much you took out. Then over fill it about half a quart.
Warm the car up, then remove the drain plug while the car is running. Any excess fluid will drain out.
When the fluid stops dripping, the ATF fliud level is correct.
Drop the car and it is ready to drive.

Another tip. Get exhaust heat wrap and wrap the exhaust around the area where you are working.
The stuff is really cheap and will protect you from getting burned. Well worth the 10-15.00 to not get burned.

SgtMajUSMC(Ret)

I paid $624 to have a dealer do the latest TSB #18-NA-355 with the new Mobil blue label ATF.

$8.51 per quart x 24= $204
3.5 hours labor=$420

I watched him do it and it took that amount of time following the TSB procedure exactly. The TSB states 1.6 hours. That is what GM reimburses the dealer if done under warranty. Two buddies had theirs done under warranty and both took the same amount of time within 30 minutes give or take.

Gearhead Jim

Doesn't the new procedure require flushing the fluid, at least on some cars, with a particular machine? A single drain-refill would leave a lot of the old fluid still in place.

For a while, the old procedure involved a drain-refill three times instead of once.

Also, the trans fluid level is indeed checked by the dripout method, but supposed to be within a certain trans temperature range. Just driving ours around the block a couple of times will bring the coolant and oil up to temp, but our A8 will still be below the checking range.

SgtMajUSMC(Ret)

Yes to the machine flush. Three times with 24 quarts total and the pan gets dropped and cleaned three times also. Car gets run in between flushes and shifted following the procedure laid out in the TSB.

Mike_Red

I went on a 1500 mile trip last week. After a few hours of driving (3+) the temps got high enough and I was experiencing the shudder. I have a range device so it stays in V8 all the time. It was severe. Sometimes it was so bad I thought the windows would crack. I was going to just look for a dealer in Miami but I decided to drive it home. It still did the shudder. Today I took it to my Chevrolet dealer and reported the shudder. They were familiar with the TSB and knew how to fix it. They called me a few hours later and said they couldn’t duplicate the problem. I told them to please try again and I promise it would happen. Nope. Nothing. So I went and asked them if the tech would ride with me and use his computer to get the readings. It took a while but we finally got the trans up to about 130*. It started to do the shudder. #victory Anyhow. They are now performing the fluid change. I really hope this fixes it. No way should a 100k car have a shudder that is not correctable.