TSB Seems To Fix 8-Speed Automatic GM Transmission Problems
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We’ve covered the problems of the eight-speed GM transmission on numerous occasions. In fact, we cover a class action lawsuit brought against GM back in April, complaints from owners, and even a recommendation that GM replace the eight-speed altogether with a new unit as quickly as possible. Now, GM Authority has learned that there’s a new fix that seems to be alleviating the eight-speed’s shifting woes outright.
As of July 8th, 2019, GM began using a new type of Mobil 1 automatic transmission fluid for the troublesome transmissions. Customers that complain of shuddering and harsh shifting characteristics in the 8-speed GM transmissions are recommended for a trans fluid flush. As of August 7th, GM dealers should also be flushing all potentially affected new vehicles on the lot.
The GM 8L45 eight-speed automatic transmission
According to TSB (Technical Service Bulletin) 18-NA-355, the latest update addresses “torque converter clutch (TCC) shudder conditions on 8L45 and 8L90” eight-speed automatic transmissions, RPO codes M5N, M5T, M5U, and M5X. Affected vehicles include Chevrolet, GMC and Cadillac vehicles, as follows.
Chevrolet
- 2015 – 2018 Chevrolet Silverado 1500
- 2015 – 2019 Chevrolet Corvette
- 2016 – 2019 Chevrolet Camaro
- 2017 – 2019 Chevrolet Colorado
GMC
- 2015 – 2017 GMC Yukon
- 2015 – 2018 GMC Sierra 1500
- 2017 – 2019 GMC Canyon
Cadillac
- 2015 – 2017 Cadillac Escalade
- 2016 – 2018 Cadillac CT6
- 2016 – 2019 Cadillac ATS
- 2016 – 2019 Cadillac ATS-V
- 2016 – 2019 Cadillac CTS (excluding V-Sport models)
- 2016-2019 Cadillac CTS-V
The issues with the 8-speed GM transmission are two-fold. First, some customers report the transmission shuddering frequently. Secondly, the shifts are very harsh between first to second, and then second down to first, especially when accelerating and the transmission is upshifting or decelerating and the transmission is downshifting. These conditions are most commonly observed under light and medium throttle applications, and as often during full throttle applications.
However, a new fluid flush appears to fix the issues, with some customers beginning to report a dramatic change in shift quality after swapping out the old juice. If the flush doesn’t fix the issue, the next step may be to replace the torque converter, which could be glazed.
2016 GMC Yukon
The issue seems to stem from “moisture content in the transmission fluid.” As such, the old GM transmission liquid is swapped for new Mobil 1 Synthetic LV ATF HP fluid. Driving the vehicle for about a week or so improves shift quality even further as the new fluid cleans things up inside the transmission and the adaptive shift algorithms relearn various parameters.
This is obviously a big deal for owners struggling with their vehicle’s eight-speed. Hopefully the new fluid swap will provide a lasting fix.
Have you experienced shuddering and harsh shifts with your eight-speed GM transmission? Have you gone in for a fluid-swap fix? Let us know your experiences by posting in the comments section, and don’t forget to subscribe to GM Authority for 24/7 GM news coverage.
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actually we (gm dealer employee) have had the new fluid for quite some time now, and we have swapped fluids 3 times, the first 8 speeds shipped with gm made fluid then we went to Mobil 1 black label fluid and now blue label Mobil 1. The newest fluid seems to have corrected the issues with the shudder almost immediately.
Would you be so kind to provide exact part number?
19417577 is the new fluid. However the fluid only temporarily fixed my 8 speed sierra. I have a shudder worse than before after about 2500 miles.
Wow. Isn’t it amazing how what seems to be such a small thing can (hopefully) make such a huge difference? For all of you out there with this 8 speed and issues, may this fix it for good!
That’s the problem when you switch transmission fluids at the same time you come out with a totally new transmission. When a problem like a TCC shudder shows up, 99% of engineers are going to look at the torque converter, not the fluid. Glad it’s working for everyone. Most people I know with the new fluid have said that the transmission is like new.
Transmission oil change does nothing
The torque converter needs to be replaced .
I truly hope this is the ticket !
And I would hope GM stands behind ” all ” the 8 speeds out there with ” this ” trouble weather under warranty or not !
So that the GM customer feels as if GM took care of the ” known faulty part ” that GM sold the GM customer !
General Motors needs to spend money to make money, paraphrasing Bob Lutz. GM is going to damage itself in the long term if they make all of the owners pay for this fluid exchange.
Stopped in the dealer yesterday and asked about getting it done on my 18 Sierra with 19k on the dash. Told me it’s covered under powertrain warranty and all he has to to do is write on the service sheet that I complained about shuddering and with that word it gets punched right through. Mine gets done next week.
That’s Great Joseph! The only reason they agreed so fast is due to all of the complaints. Make sure that your dealer knows what they are doing. My beautiful Corvette has been torn apart three times and the dealer will not admit that the problem is over their heads. They will not pay a nearby dealer with more experience to fix the problem. GM should be held accountable. I remember the good old days when one phone call to customer service would take care of the problem. Now when you call GM’s 800 number you get someone in the philippines. I am so glad the government decided to bail them out. NOT! Don’t count on the “oil” fixing the problem, but I truly hope it works for you.
GM Repaid the loan- you & GM are on your own-
What does repaying the loan have to do with the fact that they are putting out “crap” and then don’t have technicians smart enough to fix the problem?
The writer of the article needs to be made aware that it’s “Mobil 1”, not “Mobile 1.”
That’s all.
Well aware. Alas, typos happen. Thanks for the catch.
Does Shawn honestly think that the author can get all the technical details behind this TSB correct, list of all the applicable vehicles and then some, and not know that its Mobil? Obviously it was a typo… get over yourself Shawn.
Speaking of which, I think GMA is the only ones reporting on this. Maybe Shawn should focus on that and be thankful.
That. Is. All.
I have followed this closely for the last couple years since I own one of these transmissions.
It was clear at the beginning GM really did not know what the problem was. As time went on they tried fluids, new converters and even transmission replacement. In the end they discovered it was moisture being absorbed into the fluid was the issue.
GM then tried the Black now the Blue label and it has appeared to solved the issue. On the forums and dealer tech sites it has been all positive results even with higher miles. Occasionally a converter may be glazed and also need replaced also under warranty.
GM this time admired the moisture issue. They also have felt confident enough to make this the factory default fluid. It is not cheap either.
They have supplied the dealers with a specific machine to flush with.
The latest is GM has directed the dealers to flush any and all 8 speeds on dealer lots.
This is covered on the 60k 5 year warranty so everyone should be covered by time and if it is higher miles they are due for service anyways.
I can report my own experience as I felt like I really had no shudder compared to what most reported. But the flush made my transmission smoother and appears to have improved the 1-2 shift that was harsh when cold. It down shift faster and smoother up and down and not acts as should be expected.
Building vehicles today is one very difficult game anymore some of the most simple issues can be down right difficult to find and then to resolve.
The moisture in the fluids has been an issue with many companies. This has led to the greater number of specific fluids today vs the two we used to have. This has also led to shudder in other brands too. In one case it was even a leaking tranny cooler in the Audi that put moisture into the fluid.
Well I knew they had not given up and had been working on this. The question was when and how it would be resolved.
Contrary to what some think companies continue to work on issues. Generally they do not discuss them in public till it is resolved as often they are still searching for the answer.
Should have just used AMSOIL and the issue would have been solved.
scott3,
I was ok and agree with everything you said until you got to this point.
” In one case it was even a leaking tranny cooler in the Audi that put moisture into the fluid. ”
And it might be true also.
And don’t forget this ” exact ” thing happened to some of the XT4s !!
Just didn’t want you to throw one manufacturer under the bus, and not mention the ” same ” thing happened with a ” new ” GM Cadillac product !!
It also happened with many Nissan and Honda transmission in recent years.
I’m just stating that, in my opinion, as the GM is the best and spends more time on the drivetrain because that is where it counts and can not on the interior, people, that GM is no longer any better than any competition in this regard !
scott3,
And this :
” This is covered on the 60k 5 year warranty so everyone should be covered by time and if it is higher miles they are due for service anyways.”
Is this a stated service point of a GM transmission ?
60K miles ?
Just asking if 60,000 miles is the owners manual stated transmission service point ?
Because if not, in my opinion, if a customer has a GM ” known faulty 8 speed ” at 61,000 miles, and GM knows of this issue, and GM does not recommend transmission service at 60,000 miles,
GM should do this for ” all ” customers with this issue, up to the first recommended service.
Just because it took GM two years to figure this out, why should this allow then to push all of the older ones ” with the troubles ” out of the warranty period.
This very ” trick ” GM does well.
All of the customer satisfaction letters do just this, push a GM ” known faulty issue ” out of the warranty period on to the next owner to deal with.
Most people I know don’t service an automatic transmission until 100,000 miles.
“Most people I know don’t service an automatic transmission until 100,000 miles.”
That’s their own fault then. The GM trucks have a severe duty maintenance schedule in the owners manual which recommends tranmisssion fluid and filter service at approximately 50k miles.
Thanks, JackLightning :
Just wanted to know what the GM recommended transmission interval was.
One more thing than JackLightning,
Please explain GMs example of ” severe duty ”
Just wondering if driving to work at the office, and buying groceries is ” severe duty “
Severe duty is whatever you want it to mean. They probably have their own phrasing and terminology, but they’re basically saying that the normal service interval is for people that don’t care about maintaining their vehicle, while the severe service interval is for those that want to maintain and keep a vehicle running like new. It’s a rare thing for most vehicle owners to do such preventative maintenance.
Where is this information? My GMC dealer who 100% acknowledged my hard shifts in previous visits, is stating they absolutely were not told to flush 8 speeds unless they meet a very specific criteria (severe lag engaging from neutral to drive).
“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. ”
https://gm-techlink.com/?p=11127
Nothing about the fluid flush relating to “delayed engagement”, which is what you have.
Didn’t GM and Ford develop this transmission together? Do Ford vehicles using the eight speed have the same problem? If they did how did they fix it and if not why is that?
Negative. GM and Ford developed the new 10 speed transmissions which are supposed to be stellar!
The 10R80 in the Fords have been far from stellar. There are a TON of 2018-19 F-150’s and Mustangs with the 10-speed that have had nearly as many issues as the GM 8-speed had in the first few years.
Not that stellar- class action suit filed against Ford’s 10 speed.
Wonder if this would fix the 6speed in the colorado, as sounds like like similar problem. I’ve had to the dealer multiple times and flushed trans at 60K . May try this….
Murray,
scott3, knows how to fix your 6 speed also !
I fixed mine with an aftermarket tune !
GM did nothing for me on this ” known faulty ” issue.
Good luck !
Since the 1970’s, i have always replaced the trans oil in the pan, by removing the pan and wiping it clean with white paper towels, at about 4,000 miles. Then i did it again at about 8,000 miles. There is an instant difference in the feel of the transmission shift after changing just the 4 quarts in the pan. At that time, my rear drive GM cars had 16 quarts total, in all the lines, pan and in the trans. When the Mobil One was first offered for the trans, i went to a auto mechanic that had the machine to suck all the fluid out of the trans and lines, then added the few gallons of the great Mobile One. Where i lived, it often got down to minus 30 F overnight in the winter and about 105 F above in the summer, so having the best possible fluid worked fantastic. BIG TIP….when you go for an oil change, give the oil change guy a white paper towel to wipe along the trans cooling lines, as a very slow leak will show up on the paper towel. A very slow leak will burn out your trans in a commercial use situation very quickly, so ask for the paper towel treatment and look at it close.
I coincidentally brought my Sierra in for this problem 2 weeks ago after dealing with this annoyance for 2.5 years. I really just wanted to get it documented in case anything bad happened in the future, they couldn’t hold me accountable. I fully expected complete denial of any issue at the dealership. They are known for acting like they haven’t heard of well documented issues as if nobody ever complained about it before. I even said “everybody knows about this problem, just want to get it documented.” To my surprise, they said to come back the following week because they had to order new fluid. I thought they were full of crap, I wasn’t aware of a “fix”, but I went through with it anyway. I’ve been driving it for a week now and I will say it’s definitely improved. I feel like the transmission “struggles” slightly between first and second. Struggle is not the perfect word, but it seems like the fluid is heavier and you can tell. It seemingly fixed the harsh shuddering I was experiencing but I wonder if it comes with a trade-off poorer in gas mileage? I guess I got lucky with the timing though.
The first 1-2 shift of the day will have a slight bump sensation. It’s an issue that’s inherent in the design of the 8-speed.
I had the fluid change done in my 2017 GMC Canyon in May of this year (2019) and my MPG’s are up slightly. The “Chuggle” as they called it is gone, but the 1-2 shift seems to be hard at times lately. I’ll keep an eye on it.
Can you confirm a factory build date with the new fluid?
But I read on the internet that flushing fluid is bad and you should never do it as it will kill the transmission
Jon,
Don’t believe anything your read on the internet and only half of what you see. Those that state never change transmission fluid are the same idiots also say change your oil every 3000 miles. Read your manufactory’s owners manual for the correct schedule for fluid changes. For a while some manufactures were stating the transmission fluid would last the life of the vehicle but that was for marketing purposes only to brag that only little maintenance was required. Now with more work the transmissions must do with more gears and higher HP engines that easily go 150,000-200,000 miles, changing the fluid will probably always be required at least once in the life of the vehicle.
Jon – see the post by Scott3 just two posts down. BTW, I’ve never heard of any vehicle not needing a fluid change, be it oil, anti-freeze, transmission, or differential.
Is there any word on who is to pay the bill for the “fix”. Will this be up to the vehicle owner to pay?
I would think it falls under warranty since all vehicles affected are less than 5 years old. Mine was covered but it’s only 2.5 years old.
But a vehicle can still be out of warranty by being over the mileage limit, but be less than 5 years old.
Why would all vehicles fall under warranty ?
Correct me if I’m wrong, but I think the warranty is 5 years ” or ” 60,000 miles.
So you could own a 2 year old GM 8 speed with 60,001 miles and GM would not pay.
As happens every single day !
A person just wrote, that they bought a new Cadillac every year and drove it 100,000 miles.
They would own a GM vehicle out of this warranty with an 8 speed at less than 8 months.
And if they drove that many miles a year, chances are that the vehicle would be in a road gear most of the time, so it still could have this issue.
And in that exact case, they would own a 8 month Cadillac CT6, the highest price GM sedan, with a ” known faulty 8 speed transmission ” and GM would do nothing at 8 months because it is out of warranty !
And just think of this, you GM is always perfect people.
Now this person, with a one year old Cadillac, buys a new one every year, ok.
They now trade in that one year old Cadillac on a new Cadillac, ok.
You go and buy that one year old Cadillac, with a ” known faulty GM 8 speed “, ok.
You have troubles with your one year old Cadillac you just bought because you drive it in town and it shifts ” crappy “, ok.
GM/ Cadillac will do nothing for you !
And that is exactly why Cadillac has had one of the lowest customer satisfaction ratings in recent years !
If GM knows this transmission is ” faulty “, it doesn’t matter to me if its the fluid or the CUE screen.
GM ” knows ” there is a problem, fix the problem !
In my opinion.
The recomended change is
A GM Owner’s Manual will guide you to what is needed and when. Although the selected sample applies to most GM vehicles,
please refer to your specifi c vehicle Owner’s Manual for any exceptions.
• Under normal conditions, change the fl uid and fi lter at 100,000 miles (166,000 km)
• Change automatic transaxle fl uid and fi lter at 50,000 miles if the vehicle is mainly driven under one or more of the conditions below:
o When doing frequent trailer towing
o Uses such as found in taxi, police or delivery service
o In heavy city traffi c where the outside temperature regularly reaches 90°F (32°C) or higher
o In hilly or mountainous terrain
With that said if you have more than 60K miles by now you are high milage under these conditions and odds are you were towing or saw heavy duty use where it should be changed earlier.
Most people towing, HD use and have had high temps change around 50K miles that is if they service their vehicles often. The reality is most people never change their fluids in their vehicles. They drive em till they die.
I happened to have a 2016 Camaro owner’s manual handy. According to the chart on pg 333, the automatic transmission fluid and filter should be replaced every 45,000 miles.
Sorry, neglected to mention that this is the “Severe” service schedule. The normal one does not mention the automatic transmission fluid. Sorry for the omission.
GM’s normal service interval recommendations are ridiculous and too long for many of their vehicles. Their older 6-speed transmissions ran so hot under regular conditions that the transmission fluid is cooked well before 100k miles. Plus you’re circulation all the breaking materials throughout the transmission that entire time. Same with their recommendation for differentials and transfer cases. All in an effort to make their vehicles seem low-cost and easy to maintain. They claim the brake fluid is good for like 10 years — sure if you want the brake fluid to rot the brake system from the inside out.
Folks lets put this into context here.
Most of these transmissions are under warranty. You just need to present the vehicle to the dealer and they will replace the fluid and it will resolve the issues in nearl all models.
Do not be distracted by alarmest like LongtimeGMmoaner who really have little clue and just do nothing but troll and complain about eveything.
The TSB info is there. Copy it take it to the dealer and have the service done. I have done the service and it took a transmission I really thought was working well and improved it much. If you have the shudder it should make a world of difference as reported by many owners that have already had it done.
The fix also helps it shift smoother and down shifts easier and sooner.
So please if you have an issue just use the 18-NA 355 TSB to your advantage and resolve your issues.
scott3,
Folks lets put this into context here.
Most of these transmissions are under warranty. You just need to present the vehicle to the dealer and they will replace the fluid and it will resolve the issues in nearly all models, and if you are one of the many that can no longer get this covered under GM ” non ” warranty, or it does not fix your ” known faulty ” issue,
scott3, says tuff luck.
Do not be distracted by scott3, who really has little clue and just does nothing but troll and complain about everything except how great GM is.
The TSB info is there. Copy it take it to the dealer and have the service done. Unless the dealer will do nothing. In that case, scott3 says take it to another dealer, after all, scott3 says all you have is time and money for GM to use and waist.
I have done the service and it took a transmission I really thought was working well and improved it much. If you have the shudder it should make a world of difference as reported by many owners that have already had it done.
By the way me, scott3, had my whole transmission replaced by GM, before GM could even find the fluid troubles, but I, scott3, still call all of you who did not get the same treatment from GM just a bunch of complainers.
The fix also helps it shift smoother and down shifts easier and sooner.
So please if you have an issue just use the 18-NA 355 TSB to your advantage and resolve your issues.
The tsb of 18-NA-355 only temporarily fixed my Sierra. After 2500 miles it is now shuddering worse than before the fluid swap. I assume a new torque convertor will be the next step. Planning to drop the truck off later this week.
Had my 2015 C7 in on August 6, asked for a transmission flush as the symptoms were exactly as described, although the car does run. Is still under the warranty although about to expire in November. They would not repair. I told them the issue is intermittent, they could not duplicate. They said ‘warranty repair cannot be done on something that is not broken or having issues at this time’. HELP!! GM Customer Service, appealed to you before, trying again. Just because the car is drive-able does not mean there’s nothing wrong, and you have a fix but deny warranty work.
Sounds like you need to talk to a different dealer that’s willing to help you out.
Yes, I’ve had this issue on my 2018 Corvette. A transmission flush in April has so far completely resolved the shudder issue. I never had the harsh shifting.
This is all ok for owners in USA bur Cadillac only warrantry 3 years or 36000 in UK.Dealer changed fluid on my 2016CTSV three timies which has got rid of the shudder but harsh 1-2 shifts are still there on light or medium throttle,they could not get Mobil 1 fluid as GM europe do not stock it,I tried getting it via the importers but they do not stock it either so I am waiting to see what happens now.
My comments would revolve on the subterfuge local Chevrolet have told me on my 2019 Camaro convertible. To the man, they told me my transmission was within factory specs. Apparently, not only congressman lie.
Wait, a dealer was dishonest? Say it ain’t so! This destroys my faith in humanity. 😉
‘Fixed’ my 2015 Sierra DUHnali L86, 8L90, 1500 ghostly drivability issues myself…
Back on May 20, 2017 I made a GMC Dealer purchase of a Certified Used 2015 Sierra 1500 Denali 6.2L, 8-speed which had recently returned from a GM lease.
It had had ALL its `shots’, ALL the flashings and ALL the software updates were, well, up-to-date.
Drove right well (expressway) for the 50+ miles home from the dealership that Saturday afternoon. The next week?
Suburbia drivability `stuff’ began happening that you shouldn’t’ really talk about in mixed company. Still I went ahead and purchased and ported up a Diablo JUST-SAY-NO-TO-AFM as I continued my study of power programmers and performance monitors for the truck.
What types of drivability entertainment did I/we experience?
Things like falling flat on its face when accelerating from a stop; getting STUCK in a low gear following a start and go; thumps, clunks, ‘confused’ shifts.
Occasionally the drivability `entertainment’ would throw up the INSPECT ENGINE ICON.
Same codes each time. $7E8, $7EA. Transmission Control System and Lost Communication with ECM/PCM A. I would communicate these (via e-mails) to the Dealer.
At their urging I did return to the Dealership with it –once. After their inspection the recommendation was to turn it over to them for a senior tech to use as his daily driver with a real-time monitor ported up to it.
Nah, but thanks for the offer.
It’d be some serious trial, error (and some luck!) on my part that this vehicle began performing the way GM intended it to. Bottom line?
Let the bee-itches FULLY boot-up prior to STARTING and DRIVING.
For this 2015 the `pre-flight’ consists of: (1) Ignition switch to on position; (2) allow ALL instrument panel icons to check down and cycle OFF; (3) with ONLY the INSPECT ENGINE icon displayed, crank the beast; (4) following the start AGAIN allow ALL dash icons AND instruments (speedo and tach) to check down and cycle to their proper displays.
With the tach indicating engine rpms there should be NO icons illuminated in the dash unless you ain’t buckled up yet. Do it.
Enjoy your drive!
These vehicles are four wheels with multiple computers. Like smart phones, tablets, PC’s, ANY `computer’ based devices -they ALL need to TOTALLY boot-up to play well together.
I blame many of our vehicle anomalies on the GOVNORMINT. Yeah, quit trying to get 40-mpg’s out of a 5,900+ pound pick-up truck.
Get the Govnormint OUT of vehicle manufacturing and let the manufacturers have free reign again.
Next up? Figuring out how to default the truck’s MAGNETIC RIDE CONTROL to off to QUICKLY check if I’ve got yet ANOTHER Bridgestone Dueler tire with steel belts beginning to come apart…
OK thanks for sharing…. but please alert me if you ever comment again on this forum as I may need to give my dog another walk.
Thanks for sharing but I had a little problem following your advise, conclusions, and recommendations but I feel safe in saying OBama had nothing to do with the issues.
I had this done this year on my 2016 Corvette which shuddered and shook with each shift the new fluid seems to have solved the issues. Had another issue with a tranny sensor that caused a check engine light. They fixed that too. One more problem it’s offically a lemon