TSB Seems To Fix 8-Speed Automatic GM Transmission Problems1,791
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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Thanks for the information. I had my fluid swapped a year and a half ago and had it done a week ago just wondering how long before I have to do it again.
2017 Sierra, had the transmission fluid flush/swap at about 50,000 miles. The shudder was fixed until recently. I now have 102,000 miles and the shudder is back (and worse). Taking it back in a couple of days.
I have a 17 Sierra also….over 100,000 miles…put in a AFM delete at 75000….no more shudder
What is an AFM delete?
ACTIVE FUEL MANAGEMENT DELETE….prevents the computer from deactivating 4 cylinders ….there’s were the shuttering starts…I have a Range brand AFM delete….it works.
I don’t think it is just AFM, it is a poor transmission program altogether I also think the anti-collision might also affect it. I went over the top to try and save the transmission and I started with the Range module when I bought the truck brand new and I still got the shudder, I think the Trifecta Tune program is a much better solution see below all that I have done.
2018 Silverado High Country 1500 6.2L which has had the occasional hard 1-2 2-1 shift issue, as soon as I felt the shudder for the first time at 14,000 miles and immediately took it into the dealer and they did TSB 18-NA-355 triple Flush
I then installed a Dipstick for a Camaro that I bought from eBay seller blueracer1976
This required removing the heat shield on the passenger side, 3 bolts using ¼” drive 10mm, Pain in the ass with my big hands. The bellhousing bolt is tight and requires a ½” drive 15MM deep socket. The dipstick fit perfectly and appeared to show proper oil level at the bottom hash mark with engine running and the transmission temp at 160 Deg F. Once installed I was able to reinstall the heat shield. Transmission to Engine Bolt 35 lb ft
Then I Drained the oil and dropped the pan the clearance between the exhaust and the pan is tight and I used a jack to lift up on the transfer case to give myself a little extra room. I removed he pan bolts using ¼” drive 10mm, the drain plug is also 10mm, there is still a lot of oil in the pan and I made a mess in the driveway. There was some ferrous metal dust on the magnets but nothing concerning.
Pan Gasket PN 24260071
Oil filter PN 24274402
About 5 ½ quarts of Mobil 1 blue label PN 124715 19417577
One tube of lube guard shudder fix I got at advance auto parts
Oil Pan to Transmission Case Bolt 97 lb in
Plug Assembly, Automatic Transmission Oil Pan (C/K) 22.1-29.5 lb ft
Plug Assembly, Automatic Transmission Oil Pan (Y) 20.7-23.6 lb ft
I also ordered the Trifecta tune Advantage program, being an 2018 or newer I had to wait for the cable to download the security code from the engine module and send it to Trifecta. I installed the Trifecta tune with AFM delete in all modes. I noticed sport mode increased throttle response and modified shift points. ECO mode shifting was better. I just took a 1200 mile trip without any issues. Added 2 10oz Lubegard Platinum Universal ATF Protectant. Installed Shift Technology Products Sure-Cool System PN STL010
I had it done twice worked for 90000km and would come back at 350000km came back let it go for a bit then did the oil change worked for two weeks and came back . Ended up putting in a new tranny. Dealer gave me a deal 3100 for a new tranny.
My 2018 Denali with 6.2 started shuddering at around 30,000 the dealer did the fluid change which fixed the shudder until I hit 62,000 it started all over again . All the time I was running a programmer from edge with the AFM turned off so the AFM delete didn’t really work for mine . The only thing that fixed my denali was when it got stolen and hasn’t been recovered since .
I have a shatter issue when coming to a stop shifting from 2 to 1 the parks dealership in Richmond va I purchased it from wouldn’t even look at it because when they asked me if it did it all the time and I said no it does it like randomly and sometimes it do it like 25 times in a row so I said something about it at luck Chevrolet in Ashland va they done a transmission fluid flush and said it should help it but it hasn’t trying to find out what to do next
I have a 2018 truck and there are only 2 permanent fixes and they are not easy. 1.get rid of the vehicle before repairs come out of your pocket. Or 2. Drive it till it works no more. Everything that has been suggested is a Money grab it is a technology issue with the vehicles along with poor engineering and instead of creating a fix GM has spent their concentration on producing faulty electric vehicles. My opinion GM has been taking leaps in technology and with every step they get further behind on the quality they once provided. Our family has been GM/Chevy to the heart and core but the lack in quality and customer care assured us GM doesn’t care nor need our services
The flush did fix my 8 speed issues. I have driven it 6,000 miles since the flush with no problem. How long it will last is certainly up to debate. Right now I am hoping it will be a long time. 2019 Silverado 1500 LT 4WD with 49,000 miles currently.
The first flush fixed mine for about 50,000 miles, but it came back. The truck had about 50,000 miles on it at the time. The shudder came back without much warning either. Just all of a sudden and it was there again – within a week or two it was getting pretty bad. Flush number 2 cost me about $600 at the dealer, around 103,000 miles. That was a few days ago and it seems to be running smooth again, but I think I’ll get rid of the truck before I have to do it a third time.
Following. I have a 2019 Silverado, TrailBoss LT 5.3L with 34,800 miles and it has just started the shudder. I haven’t drove but about 10 miles since. Read all the posts and still don’t really know what to do?
Definitely take it to the dealer and tell them about it – they should flush it and refill under warranty, which will fix the problem, but for only about 50K miles.
Truly, there is nothing you can do. GMC doesn’t care. Faulty design and engineering. They can’t fix it. They will just string you along with band aide “fixes”. Read my more extensive explanation.
What a crying shame! Does installing the Range AFM disabler help any?
I’ve had a Range AFM installed for 25,000 miles. Works great…no shuttering..but it doesn’t get rid of hard shifts..I’ve learned how to avoid it.
relearn the clutches.
Here’s the bottom line. I have had two cars with the 8 speed transmission. 2017 CTS 3.6 and a 2018 CT6 3.0tt. With the 2017 I had it back to the dealer multiple times. 2 fluid changes and one torque converter replace…..etc. Beautiful car. Loved it. Cadillac could never get the transmission working right. Traded it at 50,000 miles. My research indicated the 3.0tt also had the 8 speed transmission, but it was a more robust version because of the 400 HP and 400 lb/ft torque. The CT6 is better, but not perfect. Had the fluid change. Still get the occasional hard shift or shudder under hard acceleration. Supposedly, both transmissions are adaptive to the driver. I have found the opposite to be true. I have to adapt my driving style to the transmission. I can drive it smoothly. Any of my family members drive it and they get hard shifts and surges. Bottom line…GMC cannot and will not fix this transmission. Period. It is faulty design and engineering. They just don’t care. GMC is just riding it out until all the cars, trucks and SUVS with the 8 speed transmission are out of warranty and out of service. Then they won’t have to worry about it anymore. I wanted an American luxury sedan. I don’t like Lincoln. I am done with Cadillac. I am the demographic they want. 56 year old Attorney. Going back to Lexus or maybe a Genesis next car.
Well, GM is doubling down on the 8 speed. They still use it on the Silverado with the 2.7T and will soon put it into the new Generation of Colorado with the 2.7T. GM claims they have reworked the 8 speed and remapped it as well. But time will tell I guess. Also anybody ready this do NOT buy the upcoming Colorado for at least two years. One thing I can say is one should never trust GM as far as quality goes. Give it a couple years. The new truck will need to prove itself and owners will have the final says if the 8 speed is fixed. Not GM.
I had the same thing happen on a 2019 CTS. They did the triple flush but I couldn’t get them to change the torque converter. Not only did it still bang in gear but it had a terrible hesitation from a stop. The hesitation was so bad that it was dangerous at an intersection or turning from a stop. I finally had to get rid of it at a substantial loss. It sure gave me a lasting bad impression of Cadillac and their customer service.
I just read this morning that GM sales topped Toyota and US sales for 2022 so I guess Cadillac doesn’t miss me as a customer.
My 2019 Silverado still has the same problem even after all the supposed GM fixes. It’s got 27K miles. Only thing we can do is public and shame GM on social media by telling people to stay away from ALL GM vehicles. Hitting them in the pocketbook is the only thing they understand. Hope they go out business!
I’ll never buy another NA vehicle again or German. Only Japanese!
Well the new Tundra is having issues with the turbo. They quit making the old reliable V8 model. Nissan will soon discontinue the Titan. Leaving you with the Frontier and Tacoma as the only reliable choices for mid size. QC issues are hampering Ford and GM. Might consider a Ram using the ZF 8 speed which is a great transmission. Or finding a year old Tundra still using the V8 that will run a million miles. If you want reliable that thing is the bomb. Sucks the gas but the port injected motor is bullet proof. 6 speed auto on that is solid like a rock.
Here’s the deal as I see it, mcopic:
If you catch the shuddering problem early and have not driven a lot with it shuddering, have the dealer execute TSB 16-NA-396: https://static.nhtsa.gov/odi/tsbs/2016/MC-10111764-9999.pdf
If done properly, that should be the end of your shuddering problem (it was for me). Read the TSB. It is ONLY for the shuddering problem, not hard shifting or anything else.
If you did a lot of driving with it shuddering, the TSB may or may not fix the problem, as other components may be damaged. In these cases, it is sometimes necessary to replace the Torque Converter.
If you are within the 5/60 of the powertrain warranty, they should be able to warranty it. I do not work for GM or any of its affiliates; that is only my opinion and experience.
Here is the key: GM dealers are not automatic transmission shops. They do not have a lot of expertise beyond replacing fluid or torque converters or whole transmissions. That is simply the nature of a new car franchise. So, when a transmission starts to do weird things, they really don’t know what to do and you start getting absurd answers to questions.
If you have already gone the warranty route and are still not satisfied, but otherwise like the vehicle, the best thing to do is find out which transmission shops in your area are used and respected by performance enthusiasts. Go to one of those transmission shops and they will fix you up. They can replace parts when needed, and may recommend things like an aftermarket torque converter, but where they really shine is in being able to tune the transmission. This will eliminate those hard shifts that so many people complain about. Transmission shops know how to do this; dealerships have no idea how to do it.
relearn the clutches.
I had the shudder problem on my 2020 silverado 1500 lt. I took it to the Chevy dealer with 32000 miles and the replaced the torque converter under warranty. That was 2 weeks ago and its drivering as it should so far.
Sounds like you had a good Chevy dealer that agreed to swap out the converter. I couldn’t get my Cadillac dealer to do that. Glad that it’s working well.
I just prepared the following to submit to our Cadillac dealer as we get it servived, when mt wife referred me to your article. The problem is still ongoing! We are still under warranty. I pray the dealer covers the problem!
“The last time we had our 2021 XT6 serviced we asked the service department to check out why we feel pulses in between shifting when accelerating. The service department said they were unable to find anything wrong.”
“Since that time the “pulses” between shifts have become more pronounced.”
“We ask that your transmission mechanic drive the car, using the adaptive cruise control going from stopped to 45 MPHto experience what we experience, then diagnose why the pulses between shifts happen, then get the problem repaired”.
Unfortunately, I have been through all the hoops with 2 Cadillacs. Some bean counter has decided it is cheaper to string people along instead of fixing the problem. The design of the transmission is faulty. Even if they put a brand new transmission in your car it will still have the same issues. It’s a shame. Both of my cars are beautiful. Ride and handling is superb. Engines are powerful and a lot of fun. Transmissions are $hit!
Damn your 21 should have the new fluid fix. All the newest programming should be part of your Caddy. Most of the major issues were remedied with the 2019 Trans fluid change with the so called mobile one trans fluid. Still GM is using this defective transmission. Its a rip off of the famous ZF 8 speed in the EU. Now that is the real deal. GM wanted a in house version of that and failed miserably.
That said I would demand at the very least a triple flush trans fluid flush while still under fluid. GM won’t replace torque convertors anymore. Personally I think the BMW makes a better motor and transmisson (ZF 8 speed) Better yet primary drive is RWD with Xdrive AWD. Made in the USA as well. And IMO, more reliable. My loaded 19 has zero issues. None.
Scott Bell Vice President, global Chevrolet gave me the opportunity to express my concerns about the future of the electric vehicles. I wrote that the future looks great but let’s don’t forget the poor bastards such as myself left with the burden of paying for the repairs of the transmission due to no fault of mine. Scott replied that he gave my complaint to the proper department which seems to have fallen on deaf ears. No one has contacted me about my concerns. O Well
When I was having problems with the transmission on my Cadillac I wrote a nice polite constructive letter, sent by certified mail, to each individual member of the Board of Directors for both Cadillac and GM. The response was that they assigned a quality representative to my case. She was useless and they kept referring back to the dealership which stated that there was nothing wrong. They did the triple flush and I was trying to get them to change the torque converter but they wouldn’t. I didn’t have the shudder. I had a bad hesitation from a stop or a part throttle acceleration. It was dangerous at an intersection particularly making a left hand turn. I finally got the dealer to have the transmission technician go for a ride with me. The car duplicated the problem and the technician told me that was normal for this transmission. He told me that he would deny that he told me this but that these 8speed GM transmissions were junk and he was embarrassed that Cadillac was using them. I never did get the hesitation fixed and ended up selling the car at a considerable loss. In retrospect, I should have at least tried to have the car serviced by an independent transmission shop to see if they could have fixed the problem.
I told myself that I would never buy another GM product after that but then a 2022 GMC HD 2500 came my way. I never would have purchased it if it didn’t have the Allison designed 10 speed, which I love.
I have a 2019 Silverado with transmission problems dealer says the new mobil transmission fluid will solve the problems.
Cost to me $804.00
I have extended warranty to 100 thousand miles wonder if they will cover this. ?
Some will…some will not….depends on the dealer…my GMC dealer wanted over 500 bucks for the flush….says it’s not covered….took it to a Cadillac dealer and they did the flush…no charge…..good luck!
2019 Z71 LT Silverado 5.3L 8L90 transmission just now at 84k miles has started surging about 150RPM at highway speeds and shuddering at times between shifts. I will be installing a new GM torque converter this weekend with the new Mobile 1 HP Blue Label fluid. Will be out around $700 on parts while doing the labor myself.
Will a new GM torque converter still have the same issues or did they do something to remedy the problem?
Not that I’m aware of. GM converter was the only option I could find in Oklahoma City area though. Well known converter shop said they are nearly impossible to rebuild, they don’t mess with them. I haven’t served the transmission at all in 84k. They recommend service at 45k under severe driving conditions, so my thoughts are the fluid has broken down and is now causing mine to shudder. The 19 and up 8L90s should of come oe with the Mobile 1 HP ATF Blue Label. I’ll be doing my trans service between 60 and 70k going forward to see if that will cure it.
OK, got it. Sure wish they made a much better aftermarket one!
Paid Dealer 800.00 for a fluid change to blue fluid crazy! 2017 CT6
$800 to fix THEIR problem. Figures
And some say that may not “fix” it????
The only real way to fix it is sell it and get away from Chevrolet. After all they don’t care.
I am 66 years old, my family, my extended family and I have been GM folks as long as I can remember. This is changing that! Between the transmission issues AND the engine oil cooler line failures, thus causing engine failures, it is inexcusable!
I have a 2019 Silverado, had the trans fluid flushed last month and the shudder is now worse than before the flush. Taking it back in again next week.