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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GM will lose their loyal owners
Brought my 2017 Cadillac CT6 TT in for the hard/ odd shifting and while braking it will feel like it is lunging forward. I asked the dealership to do the triple flush/ fluid change. They dealership said that they did the triple flush and fluid change and unfortunately did not help. It is now back in at the dealership and we requested to have to the torque converter replaced and the dealership said that replacing the torque converter is only for the shutter and they could not duplicate shuttering and they GM will not approve replacing the the torque converter because that will not fix the hard shifting. How I read the bulletin above is if the flush and fluid are changed and it does not correct the transmission issues than the torque converter should be replaced. The hard shifting literally gives you whiplash or it feel is like someone has rear ended me. People that have rode with me have asked, “what is wrong with your car” and my elderly mother is terrified to ride in the car. We are skeptical of how our dealership/GM is handling this. Do any of you have any feedback on this? We have also heard the same statements from the dealership, that this is the way the car drives and in another sentence they said that the manager has one of these cars and has the same problems. After reading all these comments I am wondering if GM/lawyers are telling the dealerships how they should respond to the customers?? Not sure if the class action lawsuit is finalized, have any of you heard the results?
While it can be a torque converter. The shifting is also likely to be the software/firmware they have on the module for the shift points, which is why some people have experienced pretty decent results with tuning. Then again it could be that they didn’t add the proper amount of fluid( which is less likely, but you never know). The dealers communicate directly with GMs engineering team. The engineers instruct the service staff with what to do. Sometimes, as seen through this transmission issue, the procedure changes a lot as new things are discovered. I’ve seen people complain about changing the torque converter not even fixing the issue. Now, if you’re convinced it’s truly the torque converter, you can try another GM dealer in your area. I’ve got some good ones near me, and the one I go to could explain it, if they said something similar.
My 2018 CTS does the same thing. Cadillac did a triple flush but I could not get them to swap out the torque converter.
Class action lawsuit will probably be tied up in court for a long time…GM is fighting it…
My 2018 Sierra w/ 62k miles had hard shifts. Mainly the downshifts 3 to 1 and 2 to 1. My extended warranty paid for a new valve body and that fixed my issues. Then traded it in 1 month later for my 2020 Sierra 3.0 w/ 10speed. They gave me $35k trade in. Couldn’t pass that deal up.
I like what I see with the 3.0. It’s not the 5.3 or 6.2, however I think it’ll turn out to be a good touch. If I went to buy one, that would probably be one of my considerations.
So far I love the 3.0 w/10speed. But with it being a new generation of truck it has some issues. Minor but that’s to be expected in my opinion. It’s been in the shop for a few days due to a recall and a engine coolant bypass valve getting stuck open. I’m loving the 22mpg city and 28 highway. Waiting for Banks to release their Derringer tune for it which will clean up the shift points. You have to learn this 10speed and understand that if u drive too slow it’s constantly shifting but if u up the rpms then it will skip gears and drive a lot smoother.
My valve body was replaced at less than 900 miles.2300 now,no problems yet 2020 RST 6.2 10 Speed.It is a used car sellers market,i highly suggest people offload their “problems”.Dealerships are low on new stock and people are buying like crazy.Plus its snowbird season…
896 what did you get for new truck ?
Does anyone have any idea on how many or what percentage of transmissions are affected? I’ve had the flush on my 2019 Colorado LT. Crossing my fingers.
Literally just stumbled across this article while having these same issues with my 2018 Sierra Denali. Just picked truck up from dealership after this fluid swap and I noticed immediately, even in the 5 miles drive home. Literally night and day difference it drives like a brand new truck
Have 2015 Yukon XL with 140k miles doing same thing…causes a 300-400 RPM shift in a pattern-like manner while going down road…also causes erratic shifting through all gears. dealer said likely torque converter shudder mentioned here, but called today and said need new tranny. Anyone else needed new transmission? What’s GM’s role for poor design?
2016 GMC Sierra w/ 8 speed with 67,000 miles. Took it to the dealership twice, over the years, due to shuddering transmission and each time they did a fluid swap. Check Engine light pops up with 2 codes, took it back to the dealership and got the call ” metal shavings in the fluid from the torque converter” and will need a new $5000+ transmission. I wonder how they knew to now check for metal shaving in the fluid. Took it to another transmission shop and 5 other Chevys and GMCs sitting on the yard with the same problem. That fluid swap is a band aid trying to keep the trans running until that 60,000 mile warranty expires. Make sure you keep your receipts!
I heard on here that there is a TSB that extends the warranty to 120k miles ?
We have a 2016 Cadillac ATS. Purchased it used, still under warranty, from a Cadillac dealer. We have had the vehicle in 3 times in 3 months for the shuddering in the transmission. The last visit to Cadillac of Chattanooga, they said that they could not duplicate the condition. I will give them one more chance. Then, I will pursue joining a class action suit against Cadillac.
Also have a 2016 cadillac ats. Bought used. Torque converter replaced after 6 months, 6 months later transmission flushed. 2000 miles left on my warranty.
Last GM car for me.
2017 Sierra Dinali 32,000 miles just change fluid under warranty having Shuttering problems at low speed and harsh shifting on occasions.
As a 2017 Silverado owner with 62,000 kms and on my second transmission, I can say that none of the fixes work. I did all of the fixes with the dealer on the original unit and got a news transmission at only 43,000 kms. After 1 year and 19,000 kms more, the clunking shifts and shudder are close to where they were on the first unit I had. The new trans unit would have had all the TSBs and new fluid as of Nov 2019, so it goes to show that the design is at fault. I recently towed around 1800 kg over 350kms and the truck shifted and ran excellent. As soon as I disabled the tow/haul mode, it performed like the first unit. The service manager asked how my trans was doing at my last visit and I had to break his heart. It was good for nearly a year, but now it’s not!
I have a GMC CanyonV-6 with an 8 spd. That shudders, up shifts too early, shifts gears back and forth on a light grade. Taking to my local GMC dealer and considering joining the class action lawsuit if not fixed. I have 17,000 miles on the truck.
Dump it. I dumped mine. It can’t be fixed. GM will screw you just like they did me.
GM customer service response
Hi Daniel, this is Serena with GMC Customer Assistance. I wanted to shoot you a quick message to let you know that I haven’t forgotten about you and I am still working on your case. I did reach out to the dealership and the Service Manager indicated that they’d exhausted all possible options. There were a couple suggestions that I had for them that I am currently waiting on a response regarding. Once I hear back I will be able to advise how we can move forward on this. Thank you for being so patient.
After 45 days at the dealer, my 2018 Sierra is drivable again. Prior to this event, I had no trouble or transmission complaints for 24,000 miles. The problem I had which developed over 3 days were shudder at highway speeds, then a hard/jolting shift from stop to about 1800rpm with no forward motion. Here’s what the dealer did: 1) Fluid flush. no change 2) valve body, and fluid again. no change 3) inhouse rebuild, no change. 4) finally a GM replacement transmission. I was told new, but ultimately the ticket says remanufactured. End result is drivable, but I am also paying closer attention to shifts and every now and then there is a mild shudder at gear change or some gear searching at lower speeds. Some of this could have existed prior to it going out as I was unaware of this defect until complete failure. Will see how this holds up.
Wow! It sure seems like your dealer went above and beyond. I wish more dealerships would do that. Congrats and good luck.
that is a great dealer that will take those steps to fix your issues. Most get told that the shudder is within specs. What area of the country do you live in, and what is your secret to getting the dealer to agree to that?
Look at reviews on the webpages. Come to the south east, we have some pretty good ones here. At least in my area in South Carolina.
East Texas. Hall Buick & GMC
I have a 2017 Chevy Silverado 6 speed V8 With 45000 miles on it. I just bought with 40000 miles on. And every time I slow down From 3-1 gear it slams or makes a clunking noise. Pretty sure it’s transmission. I’m still under warranty for the power terrain and if they can somewhat fix it. I’m thinking of selling the vehicle. Just trying to see some opinions on it. If I have to eat a couple of thousands so be it. Less worries. And less screwing around and more money out of my pocket when I’m out of warranty.
6&8 speed have the same issues. It’s just not focused on the 8 speed. Had 2001 GMC and that had shuddering issues and it was a 4 speed.
10 years and GM still can’t figure the transmission out! They’re sleeping at the switch while unsatisfied customers are leaving them in droves.
I had a Silverado with a 6 speed. I never had the high speed shuttering that the 8 speeds have but I had it in for the banging and clunking on upshifts and downshifts and when I went from drive to reverse or visa-versa. Chevy said that it’s normal which of course is BS. I finally got rid of it. My new RAM shifts like a dream.
Having the same problems with my 2017 6speed Silverado. More downshifting problems. In the shop right now as we type. Only had it for 5000 miles. I bought it when it had 40000 miles on it. Just a shame. What did Chevy tell you when you had yours serviced?
Operating as designed
They told me that it was normal. They could find nothing wrong. It’s expensive to have to trade your vehicle in before you had planned but it’s sooo nice not to have that banging. Once I can negotiate a good trade in amount on my 2018 CTS with an 8 speed that is worse than my Silverado 6 speed was, the Cadillac will be gone as well. And it won’t get traded for another GM product!!
Had a friend just had 6speed rebuilt after 245000 miles….my wife’s Cadillac has 6speed..5 years old..absolutely no problems…I had a 2011 GMC 6spd…due to 3:08 gearing it was always shifting as I live in the mountains…no problems when I sold it 90000 miles….
I have a 2015 silverado 1500 ltz 40k miles 8 speed trans
Only issue i have a occasionally hard shift from park to drive or reverse…about a dozen times….over 5 years…. guess I am lucky in a sense.
Had trans flushed twice once at about 10k miles and again from last July….
I’m still going to dump it when the 2021 ford f250 come out….im not taking chances
My buddy has a 2016 GMC 60k miles and in the shop now for everything discussed on this site…hard shift…shutdown to 15mph home mode…while on the intestate you name…been in shop for 3wks….no resolution
Its ashame I love my truck….thanks God I have 7 year 100k extended warranty