TSB Seems To Fix 8-Speed Automatic GM Transmission Problems
522
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
The new Mobil ATF fixed the shudder issue in my Colorado, but it doesn’t fix many other issues that myself and many others have had. My Colorado’s transmission is the worst transmission I’ve ever driven in my life. Right now it’s doing this horrible hard shift between 1-2 and 2-1. It sometimes feels like I’ve been hit from behind. My truck has 59,000 miles, warranty is about to expire. Buying this truck was a mistake, I wish I had known before I purchased. I’m so glad that I spent my money to be Chevy’s guinea pig while they wasted time and took forever to figure out how to fix this shudder issue. I’ll never buy another GM product, especially after reading this little gem: “GM claims the problems with the transmission do not fall under the factory warranty, as it is a design defect and not a manufacturing defect”.
I have a 2017 Yukon Denali and still have problems with the transmission lunging from first gear. Not all the time and that is the biggest problem. According to GMC it is their normal range of acceptability of performance. Without my seat belt on it would have thrown me through the windshield. Kinda like driving a bucking bronco, at times. Sometime it goes for days without doing it. Yes, they finally changed the fluid but it still acts up more violently then it had in the past. So, buy American made cars, get crap for a warranty, pay $65,000 or more for a car that is, at times, scary to drive. So, thanks for nothing, GM, for knowing you have a problem and not fixing it!!!!!!!!!!!!!!!!!
I have a 2016 Sierra SLT AllTerrain version with 90,000 miles. When I have the 4WD selector switch set on 2WD, the transmission temp goes to about 120 degrees and the shift between 1st and 2nd is harsh in both directions. I can turn the
switch to “Auto” and the transmission temp goes to around 175 degrees and the shifting is normal. Could it be that the transmission fluid cooler is keeping the fluid too cool and it works better at higher temps? I honestly don’t even know
what the “Normal” operating temp is for Transmission fluid.
I don’t own one of these trucks, and I wouldn’t know anything from the engineering aspect of it, however the temperatures seem fine. The increase in temperature probably comes from the transmission having more activity in 4WD mode. I have a 2015 Camaro RS with the LFX V6, and 6 speed auto. It seems once the transmission gets up to temperature, it favors around the 180 degree mark. The shifting sounds like either transmission, or transfer case( which is the mechanical part of transitioning between 2WD, and 4WD. On the lucky side, you probably just need some maintenance on the transmission and/or transfer case. On the unlucky side, you might be looking at some kind of repair with the transmission or transfer case. Seems more like the transfer case is to blame, but I’m not sure.
Ok, so May 2019 I take my Denali in with shuddering and hardshifting problems $700 later transmission fluid has been changed. June 2020 here we go again same issues, oh it’s the Shifting Harness $816… today I jump in my car to leave get out of my driveway and nothing! Can’t even manual shift – could have been in a serious wreck – back in the shop. All work has been done at the dealership, they had to send a tow truck. Glad my kids and I were not hurt. I don’t have to express my displeasure- bet you can guess. 2016 Yukon XL Denali.
You really need to join the class action lawsuit youshould not have to be paying for all this stuff out of pocket. Especially for their oil change I can’t believe GM is charging you for that when they are putting that in all their 8 speed transmission vehicles. Seems like the only thing that might help for awhile is to replace the entire transmission but that will probably cost you five thousand. Once you get it going sell it don’t buy GM anymore.
Excuse me Trent this Mom is probably not a child- I bet she can make her own decisions now. Are you a representative of a law firm filing suit against GM or maybe a salesman for Hyundia? Why don’t you just send her your fortune teller’s card & give her a free reading?
Just bought a 17 Yukon Denali xl with 32k on it I’ve only put 300 miles on it and its shuttering in 1st gear under 30mph I wish I saw this forum first I wouldn’t have bought it beautiful truck but 50k to shake and wobble feels li3ke a slap in the face for an American product.
Take it to a GM service department, it’s still under warranty. Make them do the transmission flush and put in the new Mobil 1 ATF. If they won’t do it, then go somewhere else. That’s what I had to do. There’s a service bulletin that instructs GM to change the fluid if it’s shuddering. Don’t let them tell you it’s normal.
I had my second flush done. The first one they used Mobil 1 ATF. The second one they used Dexron 3. I asked about it and they said the service bulletin has been changed and Dexron 3, supposedly a new formulation, is being used now
I had my second flush done. The first one they used Mobil 1 ATF. The second one they used Dexron 3. I asked about it and they said the service bulletin has been changed and Dexron 3, supposedly a new formulation, is being used now
I thought the Mobil 1 LV ATF blue version was the new fluid fix. That’s what was put in my car and fixed the shudder. What’s the new version they used in yours? Picture of bottle by any chance? Or product code.
The new flush uses a new machine as well, I think Bosch makes it. I’m already on my second “fancy flush”. The first one got rid of the shudder for about 200 miles, then I was back in the dealer. The dealer doesn’t have much control over this issue, GM refuses to address the issue with anything more than a flush, and software.
Dexron 3 was decertified at least 5 years ago. It was replaced with Dexron 6. There is no way GM would change the formula and still use the old Dexron 3 name. IMO, you either heard wrong, or they are flat out lying to you.
Took my 2016 Silverado in yesterday for the 3rd time. First two times they said they were unable to replicate what I was describing. Which was a damn lie. This time they felt the hard shift and the shudder. So they will start to work on performing the TSB and go from there.
This is my 3rd Silverado and its been a huge let down. My 2002 Silverado is still running excellent.
That’s what I heard the first time too. Second time I told them I wanted to ride along on the test drive. Amazing how they were able to duplicate it when I was in the truck.
I have a 2018 Silverado 1500 with 8 speed. Started having vibrations around 3000 miles. 1st time dealer said the wrong transmission fluid was in it. Flushed the transmission. 2nd time flush transmission and reset torque converter. 3rd time flushed transmission and replaced torque converter. Now it’s been amazing haven’t had a trouble. Until I hit 33,xxx miles. Vibrating again. Have an appointment to have dealer look at it. But I’m warranty expires @ 36,000 miles. Any recommendations??
Sounds like you may be referring to the bumper to bumper warranty. The power train warranty should still be good. I would double check with the service department, or your sales consultant though. Unless you want to get a new vehicle or something. Some dealers offer extended warranties as well. Those can get pricey, however if it covers what you need, it could maybe pay for itself. It’s all up to you though. For the new generation trucks, from what I understand they’re better, it seems like a few have some complaints, but that’s going to happen.
My 6 year extended warranty was 1,400$.Take into consideration i dropped a full point on interest of loan due to that alone,its actually about 400$.
Just found this and glad I did … have taken my 17 Sierra to the dealership 3 times since buying it and all 3 times they said everything was fine. Extreme hard shifting, enough that anyone that rides with me asks what is wrong with my truck. Dealership has never mentioned trying the flush and new fluid.
Wish I had know this before blowing 50 k on a zr2. Lots of transmission issue for 300 mile truck.
Just got off the horn with GM.Apparently engineering has identified a defect issue w the current valve body in my 2020 RST 6.2 10speed.They will not be replacing said part until the redesign of new valve body.Ive been told at this point “many weeks” is the e.t.a.Let this be a warning to those out there with the same issues/symptoms.Hopefully this helps with answers for some.
My 2019 ZR2 started having 1 to 2nd shift flare at 7000k .It was fine when I bought it new when I took it in for warranty GM says it is operating as designed nothing wrong with it.
8 speed junk.
Do not I repeat do not buy a gmc Denali the transmission is really bad on these trucks… I done took my truck in 3 times and they keep telling me it’s the fluid, so they change it twice and say it pose to do this. When me and the family driving down the road it’s a bad jerk feeling like the transmission going to jump out
I have a 2018 Denali with 6.2 and 8 speed and had very few issues before trans fluid change and virtually none since. These are not heavy duty they are light duty so treat them as such.
I had a full transmission replacement on my 17 Silverado 8 speed last December at 47,000 kms. I have 54,000 now and I still feel the clunking shifts and the takeoff from park to reverse/neutral. I don’t know if there’s additional software “fixes” after December 2019, but even a full replacement unit didn’t remedy the situation. These units must just have a design flaw that can’t be fixed. Unless GM can work some magic, I think this will be my last GM truck.
Anyone with newer vehicles that should have the upgrades from the factory? If so do you have enough miles to evaluate it to determine if it’s an effective fix?
There is an easy way to get some money back for your troubles. 1800 lemon law. It took approximately 8 months. Do everything they tell you to do. You will get something for your troubles if you have a solid paper trail. I got enough money to basically pay down my truck loan enough to walk away from the problem. Lawyer told me to keep it and just keep taking the vehicle back. It’s under warranty they will eventually fix it. Or it will blow up.