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.
- Sweepstakes Of The Month: Win a 2022 Corvette C8.R IMSA GTLM Championship Edition. Details here.
Sponsored Links
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.
2015 refurbished trash-anny –
Did the whole dealership thing until out of warranty – only got the flush out of them. At 100k it was starting to act up again, even with a plug-in AFM delete module running since about 60k. So, did a multi flush and fluid/filter change myself, added a dip stick, and still use AFM delete. Now it’s throwing codes on the fluid temp module and trans control sensor (and acts up with hard-slam shifts, sluggish shifts, stalls) .
Have had success so far by carrying along a cheap harborfreight code reader and simply read / delete the codes – and magically, trans runs fine again (until next time it throws a code).
So, I have a Q: for any “pros” out there – would you be concerned at some point this trans could grenade unexpectedly by ‘ignoring’ these codes and just keep resetting as needed? Always same 2 codes that are reported here due to ‘failed?’ sensors. ACTUAL fluid is fine, temp fine, ZERO debris in old fluid and filter.
’16 Sierra AT4. My mechanic suggested changing all the U-joints. $500 later didn’t seem to make much of a difference, but after a few weeks the low speed shifting CLUNK went away. Very strange… either way not happy with the 5.3 and 8-speed so traded my Sierra for an Escalade with the 6.2 and 10-speed. What a world of difference. So much smoother shifting and much more power.
Guess what??? This isn’t just an 8 speed issue.. I have had this issue in my 2015 GMC Sierra 1500 5.3 6 speed for a very long time. This trucks are absolute junk. and the customer service from the dealers and corporate are disgusting. They lie right to your face knowing good and well that THEY have a big issue on their hands, but tell you that YOU have an issue and this is how much it will cost you. Transmission runs way to hot, cause poor shifting, reduced acceleration, shudder, and the worst is when I am applying very light throttle from 1-4 speed it acts like it doesn’t know what gear it should be in and starts searching. This causes jerking and clunking as it search’s. I just happened to notice recently that this occurs most often when it’s switching from “V4” mode to “V8” mode. Anyway, transmission failed, Had my transmission replaced and had to foot the bill. They installed a new transmission from the factory (included torque converter, trans computer, and the trans). I went and picked it up and the torque converter failed within the first 2 miles. So they had to “flush it”. That didn’t work. So they then replaced the torque converter. Fast forward to now, I have added 45,000 miles of driving and it’s making terrible shifts again, clunking, etc. point is, 6 speeds have problems as well.
Side note I drove past a transmission shop In my town and observed 10 of the 13 vehicles out front waiting to be serviced where GM products. All different models. These people are selling garbage at premium prices. Disgusting humans.
I had a 2014 5.3 with the six speed and although I didn’t experience the shuddering that my Cadillac and Corvette A8 had, I had an extremely irritating clunking and banging with P-D, D-R, 1-2 & 2-1 shifts. I was told it was normal but I never had any other car out of my 50+ cars do that so I’m not sure how it can be called normal. I now drive a Ram 1500 with a very smooth shifting 8speed and just ordered a Ram 2500 also with an 8 speed. GM lost my loyalty due to their crappy transmissions.
I bought a 2013 Ford Fiesta Titanium new and at 6k miles the manual/auto transmission was making a loud scraping noise and leaking oil out of the front seal that ruined the clutch packs. I took it to the ford dealer I bought it from the the service manager said that’s normal without even looking at it. I asked if there was a lot of ppl having trouble with the trans and he said he had never seen anyone with a problem with that trans. So I got a tech to drive it and he told me before we got out of the parking lot that this was the worst one he had seen. I went to the chevy dealers next door and traded it for a C7 with a manual trans. Now I have a 2020 Colorado with the trans shudder at 14k miles. He oil flush has helped so far. Being a machinist for the last 30 years I would think that being some ppl don’t have trouble with their GM 8 speeds that it’s just bad quality machining from who ever makes the trans for GM. They aren’t holding the correct clearances and no one in quality control is checking the tolerances. So it might not help to buy a new trans or torque converter till/if the problem is corrected. I think GM is putting it off in hopes we will just go away after our warranties run out. I wish the Colorado had a manual I could put in it. Summit Racing sells a torque converter for the Colorado with a disclaimer that it won’t fix the shudder problem…So the +5 year old problem still isn’t fixed..
Of course GM is slow playing this until all of the warranties are expired. I believe that there are only two types of GM A8 transmissions: Those that have had problems are those that are going to have problems. Besides this forum I’m on several others (Corvette, GMC/Chevy trucks) and it doesn’t matter how many miles are on an GM A8 vehicle. Some get the problem early, some get it after 80,000 miles or more and some get the dreaded shudder, have it remedied and it comes back many miles later. What a crap transmission from a crap company that couldn’t care less about their customers.
The dry dual clutch from Ford was bad from the get go. Even engineering told upper management that it was a bad design. But they went ahead and put it into production anyway since they did not want to delay the launch for the Fiesta/Focus. There was a class action and a settlement that offered a bit of relief but it was not enough. IMO, that catastrophe was a big reason Ford quit making cars. As for the 8 speed it was GM’s lame attempt to copy the ZF 8 speed design which is probably the best automatic on the planet. But they failed miserably. And they have had issues with it from the start. Messing up in everything they put it into. Including the vette, camaro, Coloroado, Cadillac etc.. And that idiot CEO Mary Barra keeps doubling down on that crappy ass transmission and even put it into the Silverado with the 2.7T. Although I do feel they will likely draw the line on the next gen Colorado and will put the 10 into that. Because the issues with the 8 speed with the Colorado are legendary. That truck is wildly known to be very unreliable. And mostly because of the transmission. I actually put an order to have a colorado built in 2019. And found out shortly after about the issues. I begged the GM at the dealer to give me back my deposit (1K dollars). And surprisingly,he returned my money thank god. Even if he had not I would have not keep the order. Yeah I knew I would have lost even more if I had taken that headache POS truck. GM= government motors. They have not learned their lesson. I avoid the brand like the plague.
Eureka. I found the long term solution to the transmission problem. Sold my 2017 Canyon and bought a new Ridgeline. It really is unbelievable how much better the Honda transmission works. Problem permanently solved.
My 2017 Escalade is now shuddering and banging when shifting from 1-2 and back. Does any of this hurt or affect anything if you just leave it alone and consider it an annoyance? I’m just not sure I even want to attempt to have it fixed with all the horror stories I’ve just read. I may just continue to let my girlfriend drive it, as she doesn’t know the difference anyways lol.
Just took my 2018 (45k miles) Sierra in for the “fix”. I am very surprised they are not “dropping the pan”. Maybe I am old school, but that used to be the first step for anything transmission. They said the took samples of the fluid and no particles were found that would indicate the need to drop the pan (and change filter?)
I think they just hook their pump up to your cooler lines and flush the system that way.. Easier to put on their bandaid fix…
Show them the service bulletin.
What is the TSB number? This the one about the fluid change?
Had enough of my ’16 Sierra 1500 (with the 5.3 and 8 speed) that I traded it for a ’20 Sierra 2500 Diesel with the 10 speed. So far, so good.