TSB Seems To Fix 8-Speed Automatic GM Transmission Problems
Sponsored Links
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.
Sponsored Links
GM suggested the flush to fix the shudder and hard shifting on my 2018 GMC Sierra, 6.2L. 9,000 miles later, it’s worst than ever AND I’m out of warranty. Thanks GM! Another hustled customer.
What was the outcome. ?
I have a similar issue with my 2018 Silverado, but I get the notorious Transmission Shudder at low speeds(under 30mph) when the vehicle’s cold. I brought mine in 3 times for this issue. The first time I brought it in, they said it was normal. The second time I brought it in they did a transmission fluid Flush and change. The dealer said that would fix the issue and I would notice a big difference in a few days. That did not occur, the problem was the same and on occasions even worse. Finally, I decided to go to a different dealership and they put their best guy on the job. He called General Motors and they decided to replace the torque converter. I just heard from the dealer and they ordered the part that should be in tomorrow. I should have it back sometime Wednesday. I’ll let you know if that fix the issue. My biggest advice is be persistent and don’t let them get off by saying it’s normal.
What was the outcome. ?
Sorry for the delayed response. The new dealer put their best guy on the job. He diagnosed the problem, called GM and they agreed to replace the torque converter. The truck is much better since the service, but it still has a slight shudder driving it cold and between 20-30 mph. After it’s warmed up it’s great.
So, even after the torque converter was replaced, tranny flush, I’m still having the same issues. Albeit, it was much better for a few weeks. As I see it, it’s probably a software glitch that they’re working on. Anyway, I have an appointment to bring the vehicle in tomorrow and leave it overnight. I’ll keep you in the loop when I get it back.
I started to experience the shudder in my 2017 Colorado at the end of October, beginning of November at approximately 85,000 km (52,8000 miles). Outside temperatures were mild. As the outside temperatures dropped near the freezing point, I didn’t experience the shudder and didn’t experience it through the winter months. Now that the outside temperatures are rising, I haven’t felt the shudder yet, however, at times I can feel it getting close to shuddering. It seems outside temperature has an affect on it. I live near Toronto Canada.
Have you done the flush and relearn? Apparently the relearn has a new software update. I done the fluid flush with Amsoil ATF plus relearn through warranty and disabled AFM.
Have you done the flush and relearn? Apparently the relearn has a new software update. I done the fluid flush with Amsoil ATF plus relearn through warranty and disabled AFM.
The shudder returned with the warm weather, on my 2017 Colorado. I had the flush done today as described in the TSB 18-NA-355. My mileage is at 109,500 km (68000 miles). The flush was covered under the drivetrain warranty. I noticed a positive difference in the initial, short drive home. Shifting between gears is smoother. I will update when I get more mileage on it.
Good luck. I had my 2nd flush and a relearn about 300 miles ago. Seemed to improve the situation. Today the shudder returned, especially when accelerating in the 40 mph range.
I was excited to purchase my new 2017 GMC Sierra 1500 because I had been driving a 2002 Ford F-150 that I bought new in 2002. I love the new GMC truck designs and found a Frost White one that I loved. It didn’t take long to discover that the transmission had some problems that drove my wife and I crazy. Over a one year period of time, we probably had it in the service department about six or seven times. We tried to get them to find and fix the problems. They kept telling us that the transmission was normal and within tolerance. I told them several times that it was not within tolerance because, I couldn’t tolerate it. As much as I loved my $57,140 GMC truck with everything on it, I traded it for a 2018 Ford Expedition. It’s funny that my 2002 Ford F-150 that I still have with 463k miles on it and my 2018 Ford Expedition doesn’t have any of the problems that the 2017 GMC Sierra had. I really hated to trade it off because it was a beautiful truck. I almost became a GMC man but, I guess I will just have to stick with Ford.
My vehicle now has 20,000 2018 Sierra SLT. Erratic and rough upshifting and downshifting. Transmission flush twice, little Improvement for short while then back to the old grind. Return to dealer… technician stated he was unable to duplicate.. classic case..stall stall,stall.warranty soon expire
Have you tried the relearn? Apparently is has a new software update and has worked for me
I was able to FIX my transmission issue completely on my 2019 Colorado!!!! I had my truck in the shop 6 times with no resolution other than a transmission flush the first time. After that, two dealers just thought I was crazy. But my problem is now permanently fixed! I traded out of my 2019 Colorado for a 2020 Silverado 1500. 🙂
Unfortunately, this is a fix for all
I wish i had heard about the 8 speed issues before purchasing my 2019 Silverado. I’ve taken it in and they changed the fluid but hasn’t helped a bit. When i back out of my driveway and go forward it slams like someone hit me from behind. Looks like ill be taking it back every 2 weeks and then filing Lemon law on it.
Last winter I was borrowing a 2019 Silverado (brand new) from the dealer while they were working on my 2019 Colorado……again. It actually drove worse than my truck. At one point I would have sworn that I had been rear ended because of how violent the truck shook.
I bought a 2017 GMC Sierra Denali in may of 2017. I was very satisfied until I found out that my transmission is a ticking timebomb. My truck shudders all the way from home to work……that SUCKS GM. Now I Am trading this truck for a 2020 RAM LIMITED. I did like GMC as a Brand but not anymore. ALSO WE ARE GETTING RID OF MY WIFES CADILLAC CTS. GM KNOWS OF THE PROBLEM WITH THE TRANSMISSION AND DOES NOTHING. I CANT SUPPORT A COMPANY THAT OPERATES LIKE THAT. Also I am submitting how GM operates concerning defective vehicles to my union (Teamsters) to circulate to all or our union members. Hopefully this will save them the headache of dealing with sub-par vehicles and poor customer service.
FOLKS! Request someone to ride and drive with you. It’s your right and good business practices for the dealership. I have a 2017 Colorado 8 speed and a 2017 Silverado LTZ…. both have had transmission issues from day 1. Of course they are gonna day we can not duplicate your problems 😳 have them ride with you then offer them to drive. Then without a doubt they feel the problem
I did just that after the 5th time I brought it in. He felt the problem and they kept the truck. They replaced the valve body and did a flush. The problem came back at 110 miles later along with a 5th gear clunk now. I was told don’t come back unless it’s worse then the problem was this time. Huh?? Garbage…
I have a 2018 GMC Canyon. About 31000 miles on it. Started transmission issues. Dealer preformed the TSB. Will see if that fix the issue. I had both the harsh down shifts and the shutter.
I have the issues with my 2018 GMC Canyon. Did the flush TSB today.
Finally said – done… Gm customer service was terrible. They called me, explained the situation, said he would call back in a week and then asked me as if he NEVER TALKED TO ME BEFORE. I told him again and the next week he called saying why don’t I bring it back in a 6th time and see what they can figure out. Hah! I told him forget it I’m done with GM. I’m signed up in a class action but took advantage of the economic pricing situation and traded it in for a loaded Ram Limited EcoDiesel and … wow. Wish I would have switched sooner…
How do we sign up for the class action lawsuit?
That’s a good question?? How do we??
That’s a good question?? How do we??
try Krohn-Moss atty’s 312-578-9428
Google class action lawsuits re: GM 8-speed trans….
You can’t get into the class action right now. They’re already far into the process.
I had my 2017 GMC Sierra tranny fluid changed because of hard shifting complaint but tranny still shifts hard from 1st to 2nd, clunks when downshifting and shifts irregularly. Watching Class Action lawsuit to see it there is a legal resolution. Hard to believe GM has not moved forward in finding a solution.
How can I find out more about the class action lawsuit?
Class Action lawsuits.com….enter GM TRANSMISSION
I’ve had all the same problems on my 2017 Sierra 8 speed transmission that all of y’all have had….very hard shift from first to second just like I was rear ended….and from second to first same issue…truck shifting very rough….had actual transmission mechanic ride with me…he agreed with me, but nothing done as usual….had service manager ride with me….duplicated problem, but evidently, after 50 years of driving, I don’t know how to drive any more…..BS….
I bought a redline 2018 RS Camaro and have the problems you mention when I first take off in low gears. I brought my car in 3 times and was finally told this is normal by GM. …WTF…I do believe it’s related to the torque converter. The dealership in West, Texas did nothing to help me resolve the situation. I will never buy another car there and hope nobody else does either. If I didnt love the car so much I would have rid myself of it long ago. It will be the last Camaro I drive.
don’t worry, Gm corporate won’t do anything either except act surprised like you’re the first person the ever say it’s an issue… a “shocking” revelation… they might recommend you take it to the dealer to see what they can do even though you took it there 3/5/8 times already. Useless… I said it before and I’ll say it again… I ALWAYS was a GM guy and switched to Ram. So far, much happier. Maybe you would like a nice challenger… haha!
I bought a 2018 Silverado High Country new with the 6.2 and have heard about the issues, I get an occasional hard shift, or delayed engage. my issue is in 2018 the reduced the powertrain warranty from 5 years to 3 years if I’m not mistaken, I currently do not drive it that much and it only has 10,000 miles. this was to ne my last truck and I plan on pulling an RV with it and travel once I retire, obviously it will be out of warranty and I am concerned that I will stuck with a huge bill when not if but when it fails. I’m considering trading it in while it is still worth something:(
Dan – the powertrain warranty is 5 years or 60,000 miles, whichever comes first.
I have a 2016 GMC Sierra extended cab 72,547 miles on it and the transmission went completely out this past weekend. It’s in the shop waiting for the price quote for repair probably tomorrow. Not looking good. I have a 2005 Chevy Silverado that went more than double the miles of that before the transmission needed repairs