TSB Seems To Fix 8-Speed Automatic GM Transmission Problems1,789
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.
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.
- 2015 – 2018 Chevrolet Silverado 1500
- 2015 – 2019 Chevrolet Corvette
- 2016 – 2019 Chevrolet Camaro
- 2017 – 2019 Chevrolet Colorado
- 2015 – 2017 GMC Yukon
- 2015 – 2018 GMC Sierra 1500
- 2017 – 2019 GMC Canyon
- 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.
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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I have a 2019 Cadillac CTS. I noticed the hard shift almost immediately. The salesman did not deny the hard shift, but said it was normal. I have had the car serviced 4 times since then. The latest effort is to replace the trans wiring harness (or something along those lines). The trans fluid was the third attempt to fix. I am particular about my cars, but my wife, who doesn’t know the difference between a Yugo and a BMW, notices the hard shift when driving in a parking lot. The hard shift at low speeds creates a hazard when pedestrians are around.
If this is the best GM can do, GM should not be in the car business.
I agree. It sounds like how my 2018 CTS was.
Any new news on this issue? Have a 2017 truck with the 6.2L shuddering and harsh shifting. Just found this thread and was wondering if there has been any new updates? I have flushed it with the updated fluid and it helped for 5k miles. now worse than ever. Also just did all the relearns with no change.
Nope. Nothing new. The GM 8spd transmission is still crap. Some get lucky and the flush helps permanently. Others get a hiatus of “X” amount of miles but it comes back either the same or worse. Others get frustrated and get rid of their GM vehicle with the faulty transmission and it will sit on some used car lot and some other poor buyer will end up with the problem.
Sounds like your torque convertor is toast. Too much shudder causes metal shavings and etc…. down hill from there. Most amazing thing is they still put this turkey trans on new full size trucks with the 2.7T. Instead of just dumping it they are doubling down. You probably out of warranty now. If not get the TC replaced. Get it running smooth some how and sell it or see what you can get on a trade. Used truck market has never been so good. Never been a better time to dump a clunker.
I cannot believe GM is still putting these garbage transmissions in new vehicles. I had mine flushed twice, but the shudder and hard shifting came back. The 1-2 shift was ridiculous. I was out of warranty so I traded it in. I’ll never get another GM vehicle. All they had to do was make things right, and I would’ve stayed with them.
I had my 2017 Canyon flushed 3 times. I did seem to help the issue but did not cure it. Finally got a converter replacement and it is getting better on the shudder, not totally cured, but much better. Harsh shift from 1st to 2nd still happens.
Nothing new….but install a AFM delete and get rid of the shuddering…..have mine since April….works good….but still hard 1-2 shift
Find a good automatic transmission shop (local performance car enthusiasts will know who is good) and get them to tune the shifting for you. This is not a big deal for a competent transmission shop.
Ok so strike three Chevrolet!!! We’ve had a 2017 Silverado z71 we’ve had a 2017 Colorado z71 and now the 20 Colorado z71….. went they the so called fixes with the 2017’s was assured the 20 Colorado wouldn’t have the same crap transmission yet here I am at 14k miles and it’s happened 3 times in 2 weeks the studder when taking off just like the 17’s started… done with Chevrolet! Moving on to Nissan! I WAS a die hard Chevrolet person for 30 years but I’m done!
I was a Chevrolet/GM man forever. I’m done with them too. I traded my Silverado in on a Ram and never looked back. I love the truck and the smooth shifting transmission. 👍🏻
Because Dodge put the German ZF 8 speed. Instead of GM trying to in house one they use a proven trans.
Just had mine flushed again, they said this time the fluid will work. Again! Running out of warranty, I think it is a strategy.
Count me in as another victim of the 8 spd transmission shudder and hard shifting. Have a 2015 Escalade with 90k miles on it.
We dealt with the hard shifting mostly from gears 1-2 ever since we bought it a couple years back. Had a dealer test drive it a couple years ago and said it was “normal” and offered to do a flush for several hundred dollars. This is before I started to research this issue and I declined as they said there wasn’t a guarantee it would eliminate the hard shifts.
We lived with it until just recently started getting the violent shuddering – especially on inclines. Took it to a different dealer and they diagnosed it as a bad torque converter. Fortunately I have an extended warranty that covered most of the $2500 replacement cost. I assume they used the new fluid with the repair, but forgot to ask.
Picked it up today and shifting is smoother than ever. Knowing the many, many other cases of this recurring after multiple flushes and new torque converters I am cautious to assume this problem is gone. Hoping for the best.
Sounds a lot like a missing check ball in the valve body. (must have been forgotten during a lay off event) Usually harmless to the transmission, but will cause hard 1-2 shifts. Cold or first drive is the hardest. When parked the fluid is able to drain completely out of the passage way. The first 1-2 shift has a tiny delay as that air gap is being filled. In the winter the shift will be even slower the colder the fluid is. The shudder feeling, The engine is lugging. Poor base tune with AFM, and a throttle by wire so nerfed it barely moves during normal driving.
A good cold air, or just k&n filter, throttle commander<–Even the cheap ones. and a decent tune/calibration. You will have the driving experience that your dollars paid for.
Your completely wrong on both fronts, Engine never lacks power and that ball check is still there, i saw it with my own two eyes and the trans shop when they took mine down.
I have had considerable experience with this 8 spd transmission. I had it in a Cadillac 2016 ATS-V, and 2015 Corvette Stingray, which I traded on a 2017 Corvette Z06, and my wife’s 2015 Yukon Denali. The shudder was distinctive on the Cadillac and on the Stingray.
Both were cured by the TSB recommended Mobil 1 flush. The Denali hasn’t exhibited the problems yet but if it does I will have the flush performed on it too. In the case of the Cadillac my dealer quoted me nearly $800 for the flush, but my local Chevy dealer performed it under warranty, no charge. So if your dealer refuses to flush yours under warranty find another dealer, who might provide the service under the TSB.
Nice..My Silverado had 47k when shudder started…I brought to Findlay GMC IN BHC AZ, they said trans warranty expired, but did an excellent job…well worth the money…my time and happiness are far more valuable than time consuming hassle to get fix covered by GM..my 1966 Riviera GS sold me on GM wish I never sold it…my wise Father told me if engineer said you needed 4 bolts..Ford wanted to use 3… and GM wanted at least 5
I had the shutter problem quite bad . My dealership replaced my torque converter and many other tranny parts. (over $ 2000.00 in parts ) under warranty. I just have this strange feeling the problem is just going to re appear after about 30000 k. when my warranty is expired. It still shifts a little clunky from 1 st to 2 nd but after i leave my driveway i go straight down hill, so maybe that is why? Just wondering if anyone has had their torque converter replaced and then the problem showed up again ?
Murray I have had the flushes torque converter replaced along with wire harnesses and the problem came back with a vengeance. I have had a transmission specialist diagnose the problem and yet the GM dealerships and GM manufacturer will not do a thing even with the extended warranty I have. They hold no responsibility for their garbage and as a Canadian we are not valued enough as citizens to have a lemon law in effect in our country. If you have the value for a trade in DO IT and beware of GM products not just for the lack in quality but the poor customer service and outright poor choices in engineering and lack of responsibility in the products the distribute
My grandaughter’s 2018 Camaro developed this while at school. She thought it was tires. When I went to check it I discovered the very bad shutter. She had 61000 miles on it. Warranty out at 60500. Cost me 800 dollars for flush. Still trying to get GM to cover under warranty. I am 65 , Die hard Chevy man. Owned more than I can remember. May loose faith if they do not cover this. I am not to proud to give Ford a try if necessary. FYI, flush is working so far.
I’ve got you by a few years and I too was a life-long Chevy/GM man. I dumped the Silverado for a Ram, dumped the Cadillac and went German (Which was really hard for me) the jury is still out on my Stingray but so far the triple flush along with a Range device has held up. GM “triple-play” for me but they didn’t seem to care whatsoever.
2016 GMC Savanna 6.0
Shudder with transmission at low speeds
Runs fine on the highway
Did a dealer flush and replacement fluid with new Mobil ATF for trouble transmissions
Did zero to fix the issue
GM needs to own up to a recall
Sorry Mark. It’s not a very exclusive club and it’s a shame that it’s still growing.
My 2018 started shuddering at 30,000 miles . They flushed it added the new ATF and it worked fine . Just hit 63,000 and it’s back 3000 miles over warranty. Seems like they just put a bandaid on until it runs out of warranty then it’s on your dime .
I bet the torque converters that you put in, still have the problem and have not been fixed yet.. Must be hard to get a bad part corrected or find someone to make it right…
Well I think my tech and I figured out the problem, and it’s not good news. I have the intermittent shuddering issue in my 2015 Corvette and the dealer did everything (2 flushes, tsb recalibration and converter replacement) and I even bought an insert for the OBDII that deactivates 4cyl mode and replaced the wheels and new tires. All temporary. I was driving along one day on the highway and had my traction control gauge up on the display. Some vehicles have this others don’t, I’m not sure which do. This digital gauge shows how much the traction control engages when the rear wheels slip. I noticed that the guage would read 1-2% on the scale at the exact time the shuddering occurred like clockwork. I showed the tech on a test drive and had a 3rd flush performed. The shuddering stopped again, and the guage read no engagement. Again after 1500 miles or so the shuddering came back, and the guage again read that the TC was engaging intermittently at the same time the shudder occurred. The tech was amazed that no one had ever noticed this. The vehicle seems to believe there is a small amount of slip and is engaging the traction control causing the shuddering. His reasoning was (although he admitted it was only a guess) that when the fluid begins to wear, it affects the sensors responsible for relaying slip information to the TSB, making it believe there is a small amount of slip. He said it would probably take a software tweak to reduce the amount of engagement by that 2% or so to allow for the error, or a redesigned torque converter (which would be the safest way to fix the issue) which would obviously have to come from GM. GM already did this with the vette in October 2015 on all vetted moving forward and it didn’t fix the issue. He noted the issue and sent it up the ladder yesterday. I am not sure if this is what is causing shuddering in your vehicle, but it seems to be what’s affecting mine. The issue seems to start later for Corvettes because most drivers aren’t putting a lot of hard miles on it (mine started at 10000, I’m currently at 32000) but trucks that tow and/or people who drive long distances will notice it sooner because the fluid wears faster. And yes I asked whether it was different for vettes since the transmission is in the back and he said that wouldn’t have any affect because it seems to be the way GM designed their traction control systems for “safety” making them very sensitive to slip. Given GM’s track record I don’t think they’ll do anything about it. The C8s have been having gasket leaks for two years and they just now are starting an “investigation”. I won’t be upgrading to that either. Last GM junk I’ll ever buy. Maybe I’ll go for a Hellcat or Shelby instead.
Any more updates on this? I just got a brand new 2022 with the 8 speed and have definitely seen that the 1st to 2nd and 2nd to 1st shifts are really really jerky.
Go get you a AFM delete to get rid of the shuddering that will come once you put some miles on it…other than that it’s the same tranny….they never fixed it.
I’ve had my AFM off and still shudders . Been flushed and changed fluids under warranty once . Stopped shuttering for about 30,000 miles and it’s back . I turned off the AFM after the first flush .
You said it, “they never fixed it” In fact, GM has doubled down on the defective unit and put it into the full size with the 2.7 turbo. It would not surprise me that they will put it in the next generation Colorado which is too bad since it looks to be a great update. About the only other thing people try is to remap the transmission with the trifecta software which costs a few hundred. With that it changes the shifts points, kills AFM etc.. However the best fix is to avoid anything with this rotten transmission. The only good one they made was the one with the duramax 2.8 diesel with their bullet proof 6 speed. So what does GM do? They quit offering it. And shut down the plant that makes the 2.8. The only good one they had.
I’ve been reading the comments regarding transmission issues and fixes. I have a 2016 GMC Yukon Denali 4X4 with the 6.2 V8. Vehicle had 21K on it in 2017 when purchased. I currently have 126K on it and still have an unresolved issues. At 40K+ it began shuddering. The dealer dumped fluid (doubt its the new stuff) and added new with new transmission gaskets. All is well; or, so I thought. I occasionally would get the jumping and hard shifting; which is still present. At 70K+ the shudder came back. Replaced torque converter. At 103K (I have extended warranty thru 124K) it was jerking with hard shifts. They never did fix it then. They were going to check and see if it would be covered under extended warranty. (Charcoal/evaporator canister had previously been replaced under warranty) I put a cheapo performance chip on kit which smoothed out the shifting; but, still had the occasional hard down shifts and sudden accelerations. At 107K the AC condenser went out. Had to pay for that. Pulled chip at that time and haven’t put on back on yet. At 123K the shudder came back and they replaced the torque converter again. (Under warranty) After 300 +/- miles while going up a backroad hill the vehicle jerked hard and I lost power. I had traction control lights and low power mode lights on. Noise from vehicle sounded like ABS system was on//or there was a gear stripped. (I have video of noise as it is now consistently inconsistent) Had a code (can look it up if necessary) that indicated one of the following: ECU needed to be re-programmed; weak battery, ECU needs replacement. I finally got it to a market after driving 7 miles from the middle of nowhere to an area where there were people. After letting the vehicle sit and cool down for about 15 minutes I started it up and the code was gone. I drove it to dealer the next AM. They kept all day and 1/2 the next reprogramming ECU. After another 300+ miles I got the same noise (no codes) going down a hill when the Hill Hold kicked in and downshifted. This time the tach dropped to 1K and speedometer dropped top 10 MPH. Same noise as before. I was going over 60. Once I pressed down on the gas pedal the engine kicked back in and I get a hard jerk from transmission. Tach & speedometer back to normal. Since then it will occasionally downshift hard to low gear and I get the same noise. Now it sounds like a stripped gear. There is more to the story and the dealer keeps stating that it isn’t the transmission. They think it could be the transfer case. So, they asked me to run kit in 4X4 hi in city driving for a few days. I did that and never had an issue other than hard downshifts on occasion. After 49 miles of city driving I put it b ack in 2 hi. Drove 19 miles of mixed city and highway miles; primarily city. It did the same noise at the final down shift (hard) five (5) times in those 19 miles. I have advised the dealer and have not heard from them, yet. I expect to hear from them by tomorrow. Whether I do or not I driving up there (30+ miles 1-way) and telling them I need it fixed. All electrical connects are tight; all electrical components test OK; and, a new battery was installed. (Old battery was 14 months old) All confirmed by a third party GM dealer out of state while traveling. They sujspected transmission especial.lly sion ce I’ve had two (2) torque converters replaced throwing m etal all thru the transmission. I’ve driven close to 3M miles in my lifetime so I’m not new at this game. I use this vehicle for business and travel to job sites. I have been reluctant to travel long distances due to this issue. This is getting ridiculous!!!!
We have had our 2019 GMC Sierra to the Dealership twice now in the last few weeks, they did the transmission flush and reprogrammed the transmission. The fluid that came out was almost black ugh. I am so extremely disappointed, our truck slams into gear, or lunges forward, or sometimes as you sit at a light it will feel like the person behind you has rear ended you. It always made a shudder as well as other strange things when you are staring and stopping. These things all involve jerking motions. load clanks, surging forward without pressing the gas, when you would stop, it would try to keep going. I did not understand, so when we took it to them, we just tried to keep it simple, we chose to tell them it was slipping, missing gears. I did not want a lot of information; it confuses the dealer and never helps our situation. Now I read these bulletins and see so many with all these same issues that we have had with our beautiful truck. I drove a rental a few weeks back and it was so smooth, the shifting and stopping was like a dream, I was in shock, then I was angry that I had not just camped out at the Dealership. These transmissions appear to be unsafe and in need of replacement and because there are so many of them out their GM is not willing to just do the right thing and recall them. I am now trying to figure out where I stand and where I go to get help with our situation.
The shuddering is mostly resolved with the fluid flush. The hard shifting etc.. is most likely the torque convertor. If your in warranty, I would press them to replace it. Its expensive. GM will try to drag you along until you have to pay out of warranty. If you resolve your issues I would sell it. The used truck market has never been stronger. IMO, their 8 speed is knackered. GM’s been working on it for years but the mapping will never be good. Some have purchased the trifecta tune and remapped their 8 speeds and turned off the AFM (cylinder deactivation) and say it improves the shifting behavior ALLOT. It will be interesting to see if the next gen uses the 8 speed. I know they use it in the Silverado with the 2.7 turbo so it seems Mary Barra and gang keep doubling down on that crap-fest transmission.
They are unsafe in some cases Valerie. I had a Cadillac with the 8speed that did the same thing as you’re describing and I couldn’t get Cadillac or GM to remedy the problem so I eventually had to get rid of it, at a considerable $ loss. I’m in the market for a new truck and it’s either a Ram or a Ford. Never again will GM get my money.