Don't believe there is a fix for the GM 8L45 transmission.

 

I have a 2016 CT6 3.0TT with 20K miles.

All was OK with the transmission until about 18K miles. That is when the rough shifting started happening. That got me concerned since the car is on lease and I was seriously considering doing a buyout at lease end this coming June.

So I had the car serviced about 6 weeks ago...they did the "synthetic fluid" change described above along with the "learning" procedure. All is now fine with the transmission so far, in fact it seems to be performing better then ever.

Frankly I did not have much faith that it would work but so far so good.....although admittedly it is too early to know for sure.

It is also curious that the lengthy thread on transmission problems has been suspiciously quiet of late. Is this "synthetic fluid" cure really some sort of magical fix?? Seems hard to fathom that the solution would be so simple. Will it stick?

And now I have a dilemma that I quickly need to sort out regarding a buyout at lease end. I really like the CT6 otherwise and was considering the 2019 with the new tranny.

 

It is also curious that the lengthy thread on transmission problems has been suspiciously quiet of late. Is this "synthetic fluid" cure really some sort of magical fix?? Seems hard to fathom that the solution would be so simple. Will it stick? And now I have a dilemma that I quickly need to sort out regarding a buyout at lease end. I really like the CT6 otherwise and was considering the 2019 with the new tranny.

I suspect that the transmission threads have become less active because many owners have given up, others have traded out of the brand, and others, like me, have gotten rid of their gawdawful 2016-18 CT6's with the clunking 8L45 transmission and upgraded to the 2019 with the 10 speed. This is a solution that I highly recommend. So far, the 2019 CT6 with the new 10 speed is a very nice car. My first two CT6's were not so nice and are probably lurking about in some used car lot or auction.

If there was a simple and inexpensive 'fix' I doubt that so many CT6's would have been bought back by the manufacturer. It would have been big news here if a fluid flush was the solution. If anyone finds a bulletin, please share with the group.

 

Last month I bought a new knee and I had it installed earlier this week.... so I have absolutely nothing to do all day but play on the internet.

That said, there is so much confusing information out there that I am no longer sure that the CT6 is even a GM product... BUT....

The best I can gather is that a problem was found on some internal parts. These parts were "glazed", or covered in varnish. The cause is thought to be heat related as some have found internal trans temps upwards of 180*f. The new fluid is thought to be more heat resistant.

If you check the forums of the other platforms that use this transmission, Feb 4th seems to be the magical date for this fix. 0% of those that have done the triple flush and new fluid have had issues (yes, i know it is too soon to tell).

Maybe..... just maybe, GM found a fix? And if so, would a manufacturer buyback be a good deal?

 

Here is a link I found regarding torque converter issues in 8L90 and 8L45 transmissions. I am not sure this is addressing the same issue i.e. 1-2-1 shift quality.

https://www.midenginecorvetteforum....s-recalls-and-extended-warranty-coverages/19076-new-fix-a8-transmission-shudder

 

Duffy et al v. General Motors Inc.
FILED: DECEMBER 18, 2018 ◆§ 9:18CV81726
• Read Complaint
A class action alleges two types of GM transmissions suffer from a defect that produces a “shake, shudder, jerk, clunk or ‘hard shift’” when a driver accelerates.
DEFENDANT(S)
General Motors, Inc.
LAW(S)
STATE(S)
Florida
New to ClassAction.org? Read our Newswire Disclaimer
From Florida’s Southern District comes a proposed class action lawsuit filed by six named plaintiffs who allege two models of eight-speed automatic transmissions found in certain General Motors vehicles suffer from a common defect.

According to the 83-page lawsuit, the GM 8L90 and 8L45 transmissions found in General Motors vehicles made between 2015 and 2018 are prone to manifesting a significant “shake, shudder, jerk, clunk or ‘hard shift’” when a driver accelerates and the transmission changes gears. The case claims this shudder, shake and/or hesitation may also occur when affected vehicles are accelerated in a single gear and not actively changing gears. Drivers, the suit continues, have reported that an affected transmission’s gear shifting can occur so violently that it feels “as though they have been hit by another vehicle.” From the suit:

“The GM 8L90 and GM 8L45 transmission defect is a latent defect that presents a safety risk to riders, causes damage to components over time, and makes vehicles equipped with the defective transmissions dangerous and uncomfortable to ride. It makes the Subject Vehicles unfit for their ordinary use.”
The alleged defect stems from issues within the GM 8L90 and 8L45 transmissions that cause friction surfaces, hydraulic systems and gears to function improperly, which, in turn, causes metal shavings to circulate through a transmission, according to the complaint. These problems beget further issues, the case goes on, as damage to the transmission and torque converter ultimately result in the need for “escalating repairs” to clean out the inside of a transmission, if the component is even salvageable.

“Consumers face escalating repairs that can include flushing the transmission of metal shavings caused by the defective transmission operation,” the lawsuit reads, “and which eventually necessitate the replacement of components such as the torque converter, valve body, or the entire transmission."

The plaintiffs allege GM has been aware of the transmission defect for years, since at least 2015, yet failed to disclose the alleged transmission defect to consumers at the point of purchase. While GM has allegedly known of the problem since right after the GM 8L90 and 8L45 transmissions were introduced, the complaint states a solution to the issue, much to the dismay of vehicle owners and lessees, has yet to reveal itself.


I find your post to be interesting as it appears that GM is now making a second attempt to try a different transmission fluid to correct this issue. Before the law suit Cadillac/GM was telling service departments not to attempt any further repairs to the transmission as the harsh shift was considered to be a normal characteristic of the transmission:hmm:

 

Check the Camaro6 forums for more discussion - same transmission same issue. My son has an SS, had the triple flush fluid replace reprogram thing done, seems to have done the trick but maybe too early to tell.

Sent from my Pixel 3 XL using Tapatalk

 

MHT this issue is for shudder that is different then poor shifting.

 

Go back and read what I posted. The Lawsuit is about harsh shifting and not shudder. I did not post anything that had to do with shudder.
The person that I responded to mentioned a shifting issue but referenced something that pertained to shudder. I was responding to the following:
Quote Originally Posted by Psab630 View Post
Here is a link I found regarding torque converter issues in 8L90 and 8L45 transmissions. I am not sure this is addressing the same issue i.e. 1-2-1 shift quality.

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

 

Your right I stand to be corrected . Psab630 sent the link regarding shudder. TSB 16-na-175 and 18-na-177 is for shudder and not shifting per service tech at dealership.

 

Yes it isn’t clear that changing transmission fluid will cure the shifting behaviour.

I’ve found that the issue can be easily demonstrated by using the paddle shifters in manual mode. Is everyone else finding the same 1-2-1 shifting problem?

 

Did I read this right? You can reliably replicate the shift problem by using manual mode?

This would be very helpful when test driving a used car.

 

For what it is worth.....

It has been two months now since the Mobil One synthetic fluid flush procedure was performed on my 3.0TT CT6 (20K miles). Prior to that I was experiencing increasing harsh shifting and also a subtle vibration when sometimes running in V4 mode (shudder issue?).

Amazingly I must admit, transmission performance continues to be very smooth now and the vibration in V4 mode has completely disappeared. It feels like I am driving a totally different car. If anything it seems to be getting even better with time. Are both those issues related to the torque converter mentioned above?

But do I trust this fix longer term? Not really, and there is little time to know for sure if this is a permanent fix with my lease running out in June. So my plan right now is to swap out the car for a new 2019 CT6.

 

2016 - trans valve body replaced , fluid flushed. All is well after an additional 10K miles. Drove my wife's 2017 Audi Q7 3.0 and it did a rediculous 1-2 shift clunk/lurch. I mention that only to say, the CT6 is just as good now as any car I have driven lately.

 

Did they find error/codes in your cars data before the repairs? Thanks in advance.

 

sorry for the late response. I actually never asked about codes. I just told them to fix the damn thing or take It back.

Again, a lot of different results but they have mine dialed in finally. As good as most cars (not better) but makes me love the car again. I drive It in Sport around town and touring on the highway. Also, I drive It like I stole It. The harder you drive this car the better It performs. Get one with the magnetic ride if you get one.

Magnetic Ride
3.0 TT
AWS
AWD
20" wheels

 

I'm waiting on a valve body replacement (maybe next week 'they' tell me) and I will inquire about the flush procedure. Tell me about the flush - do they have to do it multiple times? Is there a special ATF fluid used to fill the tranny at the end? Did they re-flash the computer as part of the fix?

 

Sorry to take this thread off-topic... if this 'fix' doesn't work, I'm going to see about a trade or a buyback. Not too sure what they'll do for me on a two year old car (in service date 4/17) with 15K miles, especially knowing the issues that I've had.

 

The “triple flush” procedure - what exactly does that entail?

I’m due for my first service, and as per my custom with all of my vehicles I’m having the engine and transmission flushed and filled with Amsoil Signature Series full synthetic motor oil and Signature Series full synthetic ATF, respectively.

After reading these posts regarding the new procedure, I was thinking of having the dealership perform it seeing as how my car is still under the original warranty.

Therefore, I need to know how many bottles of flush to purchase, and if they use three bottles of flush at one time, or if they flush-and-fill the transmission three times.

Thanks!

PS: My car shifts just fine and I’m very much enjoying driving it. That’s why I’m using Amsoil - I plan on keeping my CT6 for a long time!

 

The following was lifted from another thread here:

Some excerps from a GM Techlink article that announced the new TSB:

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.

Snipped paragraphs

The new fluid exchange procedure requires the use of the
DT-45096 TransFlow Cooler Flush Machine and DT-52263 Transmission Fluid Exchange Tool Kit. 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.
The new Mobil 1 Synthetic LV ATF HP transmission fluid is now available 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.
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, 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.

Anybody wanting the Techlink article PM me with your email and I will email it to you.

This I do not know for certain but is my understanding based on what I have read in several forums:

There is significant heat buildup in the CT6 transmission causing breakdown of the original fluid used. That caused a varnishing of the mechanical surfaces. The flush procedure is designed to correct that. A special Mobil 1 high heat stable ATF replaces the original fluid.

This I can say for certain:

This procedure was performed on my 2016 CT6 3.0TT (20K miles) in January, and it has very amazingly cured the significant erratic shifting I was experiencing.

Given the history of transmission problems with the CT6 (and the related impending class action lawsuits filed in 7 states to this point) I would strongly advise that you only have a qualified Cadillac service center do anything with the transmission.

 

Here's a link to the GM Techlink site with all CT6-related entries. The "TCC Shudder and New Mobil 1 Fluid Exchange" announcement is half-way down the page. The comments at the end have some additional info as well.

https://gm-techlink.com/?s=CT6

CC

 

Thanks everyone!

So the guy who, ages ago, posted that his issues went away after switching to Amsoil ATF was dead-on.

That’s why I stopped using Mobil 1 and switched to Amsoil over 15 years ago; Amsoil is the superior product. If the ATF fluid is the culprit, then had GM used Amsoil as the automatic transmission factory fill, there would never have been an issue. Imagine the money GM would have saved, not to mention the good will and loyalty of the customers they would’ve kept and/or won over. All due to Mobil’s inferior product!

 

I don't think I'd go as far as saying it's an inferior product. One guy's Amsoil change can't make that case. Perhaps it is the wrong product for that transmission, and it's being addressed. I've been lucky and haven't had any transmission issues. That said, I'd kinda like to have the new ATF as well. I just always try and follow the "if it ain't broke, don't go fixin' it" line of thinking and that's certainly a factor. I've got 89k miles and 5 years left on my CPO warranty. I'll see what happens over time.

 

Just my opinions:

My take is that if the Mobil ATF had to be re-formulated in order to perform as-expected (it was rated as being Dextron HP-compliant, after all), but the Amsoil performs as-expected as-is, then the previous formula of Mobil ATF is inferior to the Amsoil ATF. I assume the reformulated Mobil ATF is still inferior to the Amsoil, only having been improved just enough to not absorb quite enough moisture to cause the issue, but no more.

In any case,I always switch over to Amsoil fluids (i.e. motor oil, ATF, and gear lube) the first chance I get. I change my oil once a year (using Amsoil’s oil filter) and I’ve never been let down. Sure, it’s more expensive than Mobil 1 initially, but if superior lubrication prevents expensive problems down the line then it’s well worth the cost. The same reasoning leads me to always fill up with Top Tier fuel (I try for Phillips 66/76/Conoco as they advertise their gas as having 30% more detergents than the Top Tier minimum requirement). The gas is maybe more expensive, but if it keeps the engine and fuel system clean and trouble-free then it’s worth the cost.

 

Thanks to all for providing this welcome information.
As a new 2016 CT6 3.0tt owner I was shaken to read initial transmission threads detailing the same symptoms I was experiencing.

The news of a formal procedure to deal with the hard shift/shudder issue has eased my fear.
Scheduled to be performed next week and my dealer promises me a loaner as he wants to keep it long enough to verify the fix.
Fingers crossed and thanks again

 

I just wanted to note that my 2014 A6 3.0T (amazing car) had a transmission stumble under moderate acceleration when shifting from 1 to 2. It was a little irritating and I could find others reporting it on the forums. It wasn’t perfect.

So far...(knock on wood)...my CT 6 Transmission is ok. Certainly as good as the A6.

So far.

 

Thanks to all for providing this welcome information.
As a new 2016 CT6 3.0tt owner I was shaken to read initial transmission threads detailing the same symptoms I was experiencing.

The news of a formal procedure to deal with the hard shift/shudder issue has eased my fear.
Scheduled to be performed next week and my dealer promises me a loaner as he wants to keep it long enough to verify the fix.
Fingers crossed and thanks again

When the procedure was performed on my 2016 3.0TT back in January the Cadillac service dealer kept the car for 3 days to be sure that it worked. I gave them the permission they requested to allow the service technician to drive it home each night.

The procedure amazingly improved performance by about 95%. Still the occasional 1-2 stumble but no where near what it was. Then again, perhaps I am being overly critical given my sensitivity to the issue.

This has renewed my faith in Cadillac to the extent that I am seriously considering a 2019 CT6 when my lease runs out in June. My frustration there is that I have not been able to find one at any dealer nearby to test drive the new transmission. I have been waiting since January and the vibe I get is that the dealers (5 of them) do not expect to have one available any time soon. So I have been looking at the competition and comparing transmission performance.....In that regard I have concluded that no transmission is perfect nowadays...Each has its quirks. Perhaps that is due to the quest for mileage performance ratings etc,

 

Thanks to all for providing this welcome information.
As a new 2016 CT6 3.0tt owner I was shaken to read initial transmission threads detailing the same symptoms I was experiencing.

The news of a formal procedure to deal with the hard shift/shudder issue has eased my fear.
Scheduled to be performed next week and my dealer promises me a loaner as he wants to keep it long enough to verify the fix.
Fingers crossed and thanks again

When the procedure was performed on my 2016 3.0TT back in January the Cadillac service dealer kept the car for 3 days to be sure that it worked. I gave them the permission they requested to allow the service technician to drive it home each night.

The procedure amazingly improved performance by about 95%. Still the occasional 1-2 stumble but no where near what it was. Then again, perhaps I am being overly critical given my sensitivity to the issue.

This has renewed my faith in Cadillac to the extent that I am seriously considering a 2019 CT6 when my lease runs out in June. My frustration there is that I have not been able to find one at any dealer nearby to test drive the new transmission. I have been waiting since January and the vibe I get is that the dealers (5 of them) do not expect to have one available any time soon. So I have been looking at the competition and comparing transmission performance.....In that regard I have concluded that no transmission is perfect nowadays...Each has its quirks. Perhaps that is due to the quest for mileage performance ratings etc,

 

....In that regard I have concluded that no transmission is perfect nowadays...Each has its quirks. Perhaps that is due to the quest for mileage performance ratings etc,

I agree completely with Fred and it's a point that should be made. Discussions regarding transmission performance can be found all over the web and seem related to 'quirkiness' among all manufacturers' drivetrains. The trend toward eight and more gears has brought us all here, when we're relieved when we don't notice the damn thing struggling to select a gear. If it brought us 35-40+mpg I suppose it would be worth it, but honestly, the fuel economy with these piddly little six cylinder engines isn't all that impressive. I saw a comment on-line with the question, 'Why can't car makers build good transmissions anymore?' Seems like a lost art.

My first two CT6's underwent all the transmission fluid changes, re-learning crap, total replacement and they remained deeply flawed vehicles. I had gone beyond insisting that the service manager drive these things for week, so when the dealership owner finished his miserable week with my 2017 CT6, that's when sh@!t hit the fan. He couldn't get back into his daily driver soon enough.

My third CT6, a '19 with the 10 speed transmission is a significant improvement and drives and feels like a totally different model. It actually feels more like a Cadillac, so far.

 

I feel that Cadillac/GM didn’t do a poor job of designing and building a transmission; no, they unknowingly filled it with an ATF that wasn’t up to snuff. Ultimately, that ATF cost GM a lot of time, money, and good will. Mobil isn’t going to lose business over this, but GM will (and has) even though it isn’t their fault.

At the very least, GM now knows to test for this sort of thing.

If I were at GM and in a decision-making position, I’d seriously put the screws to Mobil to make sure they don’t provide just-good-enough-to-meet-the-minimum-requirements fluids ever again.

 

I just confirmed that they use three bottles of flush (hence “triple flush”) and then drain the transmission and re-fill it. Fortunately, I ordered three bottles of flush just for the transmission, so I’m good to go for my scheduled service appointment next week.

The dealership in Ohio recommended Brogan Cadillac in NJ for service, so I’m crossing my fingers that they are good people.

 

So I dropped off my CT6 at the dealer for the fluid flush this morning.
Service guy drove it and experienced the hard 1-3 shift and gave me a loaner. Got a call 3 hours later and the same guy says that his tech drove the car and found nothing. Said they might want to try a re-learn of the shifting but other than that there was nothing they would do.

Thanks to this forum I hit him with all the information regarding the history of this issue and included the link to the tech note detailing the flush procedure with the new mobile 1 fluid. I also noted the multi-state class action lawsuit and stated that doing nothing was unacceptable.
Got a call back from the service manager who conceded that I was well informed and that GM had put all of the dealers in a bad spot .

Bottom line is although he does not think the flush will help much they will do it as long as I won't hold him to the results.
He was a very candid and professional guy that fully admitted the 8 speed 8L90 and 8L45 trannys are rubbish.

Fingers crossed
Ugh