TSB Seems To Fix 8-Speed Automatic GM Transmission Problems
356
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
What percentage have this problem? I have a 2018 Silverado 6.2L with the Max Tow and I have not noticed anything except what I thought was a flawless transmission. It has almost 15,000 miles and I have made several road trips pulling a medium weight travel trailer.
I only heard about the problem when my dad showed me a newspaper article mentioning the 8 spd problem, so I googled and found this site.
GM fan my whole life, but this Yukon I bought has given me a run for my money. I have been in the Quick Lube business for 15 years and just recently stepped out last year. I bought my Yukon with 45k miles and have put about 10k on it since I’ve owned it. Performance and handling like no other, hands down, best on the market. Looks are great it feels great and sounds great, especially because I opted for the 6.2L. The transmission started acting a little funny about 58k and I didn’t mind it too much attention. But, by the time I got to 61k, it was shuttering and slipping, particularly in 2nd gear. I called the dealer and asked them, they had no idea that these transmissions had any issues. Oh well, what do you expect from a dealer. I looked on this forum to see what was going on and I saw the update about the fluid. We all have our preferred brand, but being in the industry for so many years, you learn the politics and quirks of all of them.
Mainly, when new specs it something that is already covered by an oil and manufacturers want to buy rights. The manufacturer that has been first in spec categories, with every manufacturer, is Amsoil. Don’t get me wrong, they have had their quirks, but they are minimal compared to the rest. I’m don’t have a biased opinion when it comes to oil anymore, but I knew I wanted my truck fixed. On the way to the shop it was slipping and shuttering. In my 15 years of experience I haven’t seen any vehicle have trans problems get it flushed and it fixed everything. Trans problems + Trans Fluid Exchange(TTECH)= 99% disaster, go ahead and call a tow truck. But I’m thinking at the same time I gotta do something because I’m not going to put my wife and kids in this truck and send them down I-4 at 80 mph to go to Disney and the trans dies. So I said let’s see if this works.
POINT is Amsoil SIGNATURE SERIES LV fixed my trans 100%. It has to be the one with the Blue Cap. It is a high dollar flush and finding a shop that inventories Amsoil is difficult too. It has been 1 month since my flush. AMERICAN LUBE EXPRESS, on Havendale, in Auburndale, FL, can take care of you.
Good luck
I had my 2017 Silverado 6.2L 8 speed in for the fluid change and initially, it was much better, but not fully cured. After about 6 weeks it’s right back where it was prior to the fluid swap. I’ve never had the shudder everyone is talking about. Mine shifts extremely hard from 1-2 and 2-1. It’s got a mind of its own and when it’s happening it’s terrible and consistent, but it’s not all the time so it’s really hard to replicate for the dealer. If I run the trans in tow/haul it works perfectly. I honestly think they should spend some time and adjust the shift points. I really believe it would help, but I’m sure it’s a fuel mileage concern. If there was an aftermarket tuner I would be all over it to help correct this issue. I’m about ready to sell/trade for a new truck…
For what it’s worth. I had the fluid replaced and eventually the torque converter replaced in my 2017 6.2 with the 8 speed. I had hard shifts and vibration/shutter problems. Only had 20,000 miles on it. I just gave up last week and traded for a new high country 6.2 with the 10 speed. It stickered for $65k and I paid $46k brand new. Hope the 10 speed is better. So far it’s smooth as hell.
I deleted AFM with Range it seemed to of helped with rough shifting crossing fingers. Have a 17 High Country 6.2L also swapped fluid a year ago with Amsoil ATF
I am now experiencing the truck decelerating when I let off on the accelerator. It’s like the brakes are dragging. I shift to neutral and it goes away. I paid 65K for this Denali that is a beautiful truck and the transmission is banging and shuddering and very slow shifting from reverse to forward and forward to reverse. GM, step it up and address this issue!!!! I have had it in the dealership 4 times, They changed the oil, reprogrammed it and told there was nothing more they can do. I am pissed!!!
I deleted AFM with Range and as odd as this sounds the clunking stopped shortly after and never returned knock on wood. Have a 17 High Country 6.2L
This was recommended for the eight speed transmissions,six and eight cylinders, but nothing was recommended for the 4 cylinder turbo with 6 speed automatic. My 2014 ATS 2.0 liter Turbo automatic was stuttering between 1500 and 2000 rpms. At all gears, and could be avoided by manually shifting to stay out of that range. At 89800 miles, there was no warranty and a torque converter was quoted at $2800. I told the dealer rep that we should try changing the transmission oil as was done in the bigger engines. And damn it, it worked! As soon as I left the dealership, there was no stuttering.
As it should. The problem has always been with the 8 speed. Issue exists with Caddilacs, Corvettes, Colorados, full size trucks, camaros etc.
My 19 Sierra 4cyl 8spd is about to go back to the shop for the 4th time. They’ve replaced valve body and fluid on my first and second trip in. Then the third trip in they drove it and sai nothing was wrong with it. I picked my truck up and drive about 6 miles and my son asked why my the truck was pulsing while going up an incline.
Even with the oil swap, valve body replaced I still have a new truck that was built by unskilled labor for a worthless ass company. I now have 10,200 miles on my truck and the computer said I have 7% of my front brakes left… At 10k miles? when funding allows i send. this one down the river and go foreign.
first new vehicle purchase and i couldnt feel more let down.
GM. go fuc|{ yourself. you know what you are doing isnt right but you continue. your day will come.
2019, new body Silvarado 1500LT. 8 speed.
Could feel shift to drive or reverse from park, my old 2016 6 speed you could not. Chalked it up to….its a brand new truck, all good. Now at 25000 miles. It in the dealer for loud wine, when accelerator is depressed, any gear even park, told it’s the recirculating pump.
Since it’s at dealer now, I documented the tranny shift issues, also shuddering when I do 3 point turn in heavy traffic conditions where you need to shift quickly. I have been in a rental for a week, dealer has no solution yet.
Update……dealer says whine was from a pully, not tranny recirculation pump like they assumed. The whining has stopped. as for hard shifting and shuddering, they said no codes, and tech could not simulate problems, they chalked it up to tranny is a learning/adaptive trans. Shifts from park can still be felt, at least its documented at dealer now. The rental I had was a 2019 old body with the 6 speed trans, the week I drove it the trans was perfect, shifts from park to drive or reverse were smooth as butter.
2017 Canyon. Have experienced the Shudder problem. Dealer flushed and put in special fluid. Much better now but still not as it should be. Dealer is going to replace Valvebody? I hope GMC stands behind their product!!!
I have a 2015 gmc denali with the same shutter problem. I have had the fluid flushed 3 times. Amesbury chevy in Mass. looked at it. they claimed it was the torque converter. I left The dealer ship to get another opinion. The next day the truck would not shift would just wined. I had it towed to a transmission shop. They flushed the fluid. would run but still heavy shutter. I had the torgue converter replaced with a new one. I’ve had my truck back for 3 days know and the shutter is back i am out of pocket thousands at this point and beyond pissed off with this issue.
From the reads from owners the only fix when it gets as bad as yours is a new transmission. Also, you should have used the new T-mobile fluid that came out in beginning of year with the new bosch transflo machine to apply it since that will insure no moisture gets into it. Moisture is the culprit here. Are you out of warranty now? That’s going to be a issue starting with the 15’s now. The fluid change is so complex and takes about 3 hours. Your looking at about 700 dollars out of pocket. The 8 speed is a joke. To late to lemon law your issue. Also see if your in a state that is on the class action. If so, get yourself added on the list. If you really want to get under their skin write a detailed statement and make a complaint on GMC’s BBB web site. That can go along ways. I’ve gotten thousands back in good will over the years. OEM’s don’t like bad marks on their BBB site. And when they respond which I guaranteed they will stress over and over that you know they had many issues over 5 years and multiple TSB updates. Tell them you have copies of that (there easy to find on the Colorado forums) and that you at least should be entitled to a complete flush at the dealer with the new fluid/mobile one. Also don’t drive it too much when its shuttering. It will glaze your torque convertor and it will break again. Good luck.
Just started to get the shutter about 45,000 miles after I parked the truck because my company gave me a company truck to drive now when I drive it at a constant speed 50 to 60 holding steady I get a shutter feels like driving over rumble strips on the freeway with cruise control set at 75 no issues yet I’m thinking about taking it in next weekend
Take it to Tasca in Woonsocket RI. They fixed mine, no more shudder. Hurd GMC in Johnston RI had it three times. First Fluid flush, second torque converter changed, third did nothing. Third time they had it for a month. When I picked up my truck from Tasca the service writer said the mechanic said the fluid in the transmission was brown, indicating to me that Hurd did not change the fluid and probably not the torque converter either. The new fluid is supposed to be red. Most shops are probably not changing it because it is so expensive.
My 2019 would change in and out of overdrive. Then it started almost like downshift between second and third shift change. It started off just in the morning. I had the fluid changed it helped the overdrive problem, but now the had down shifting an hard up shifting is becoming more common. Took it into the dealership and was given a notice from GM that the hard up and down shifting was normal. This will be my last GM product.
Danny
So I had my transmission replaced on my 17 Silverado. I have to say that it is much better than it was at 47,000kms. I do still notice the “bump shifts” from time to time, but nothing like it used to. I drove it in -25 degree weather today and it shifted almost normal! It’s great that I have a transmission that operates much better, but now I wonder how long it will continue to shift so well?
I had the same shutter issues with my 17..changed fluid, updated computer, replaced torque converter and none of it worked..GM eventually told me to pound said and “we cant replicate the problem”. I sold the POS. Now I bought a 2020 high country 6.2l with the 10 speed trans and after 1k miles this damn thing does it too. Should not have these issued on a 72k truck that’s brand new..
I have a 2017 Sierra with 20,000 miles and 8 speed transmission….had it in dealer 4 times now, and hard shift between 1st and 2nd is still there….this last time valve body was changed out and no good outcome….service manager said they couldn’t get problem to duplicate, so took him for a drive and showed him hard shift at low rpm….was told it is normal and evidently I don’t know how to drive anymore….after 50 years of driving, never had vehicle do this….now it’s my fault…bullsh#t GMC….
2017 Sierra 1500 with the harsh up and down shift issues. Have had the fluid flush and upgrade in October. Helped for maybe 1000 miles, then harsh conditions returned. Going back to the dealer tomorrow. When i was talking to the service advisor about the glazed converter, he acted like i was dumb and he had never heard of it. I spoke with a friend who is a tech at a dealership in Texas (i am in Oklahoma), and he said what many on here have repeated – the converter change resolves most, but at the core of the issue, this isn’t a great, smooth transmission. But some of the behavior is downright dangerous. Mine has 52000 miles and i can’t wait until i can sell it. Wish i still had my 2015 with a six speed….
I bought a brand new 2019 Chevy Colorado from the dealership in Cape Girardeau Missouri it had 0 miles on it Within the first 102 miles it started shifting hard and shuttering I took it to the dealer they could find nothing wrong and they flush the system it stopped the shattering but not the hard shifting I am now at 5200 miles it still does the hard shifting took it back to the dealership for the fourth time they said they can’t Find anything wrong with it I don’t know what to do next
This is whats troubling for me. When did you buy your Truck? They have been putting the new fluid at the plant on new production for most of this year. Yet I keep hearing about owners saying this does not always fix the transmission. Sometimes a complete trans replacement will fix the ones that seem to have terminal issues. Document your case for lemon law. Add yourself to the class action is your in one of those states. But from what i’ve seen, some cases are so bad only a replacement seems to fix the issue. GM is pushing back. Many have swore off the brand forever.
Can anyone say with certainty, can I expect the fluid change to be done without any existing problems under warranty and TSB?
2018 Corvette Grand Sport.
No GM will only approve it if your car exhibits the issue. I know. In the beginning of the year I ordered a custom build Colorado. Before it was built they had come up with the new fluid/fix but had not approved it for production yet. At that time I had discovered the calamity this 8 speed has had for 5 years. So I had asked a manager near production to put the fluid in my build. They refused. I then asked if not, could the dealer put the fluid in when the truck arrived. Again they refused. AT that time they slipped and admitted that 20 percent would fail eventually. I then told them I would no longer except the build under those conditions. 20 percent is insane number. Luckily, the GM gave me back my 1K deposit. The reason they won’t exchange your fluid is there are probably 300K plus trucks alone that need to be exchanged. This trans is so bogus that it takes a special bosch transflo machine and several flushes and probably 3 plus hours of labor. Freaking trans flush probably cost 600 dollars. That’s why they won’t do it. Also, many people who do have the issue are still refused unless the symptoms are major. They are told that “hard shifting is normal, and no fluid for them. Its crazy. I just avoid this 8 speed like the plague. Avoid GM in general. Even Ford puttng out crap with faulty powershift trans and over a million gimped owners are bascially in class action and thousands of personal civil suits. Domestic brands are to be avoided. That’s my perception of things.
Actually, the latest version (August?) of the TSB 18-NA-355 eliminates the requirement of verifying shuddering before replacing the fluid. This is not a “hard shifting” TSB. It is for the shuddering only. See it here: https://static.nhtsa.gov/odi/tsbs/2019/MC-10163890-9999.pdf
Depends on your dealer. I received major opposition the first time (15K), but I was pressuring them to replace the TC. When the problem returned (32K), they barely let me finish stating the problem before scheduling a 2nd fluid change under the current TSB. I still have 3 years of warranty so I’ll be back around 45K miles for a 3rd change … or whatever the latest band-aid happens to be at the time.
He wants to know if they will do it without exhibiting the condition. And the answer is no. It’s expensive flush taking hours from what I understand. But like you say, they will appose even those that have the conditions. If your truck is fine, there is no way they will do it.
False, if we are talking about the shuddering. A prior version of TSB-NA-355 DID require that the symptom be verified prior to doing anything, however, a subsequent revision removed that requirement. Read it for yourself here: http://andmagazine.com/talk/2019/12/17/scorched-earth-policy/
Print it out and show it to the dealer, if need be.
False, if we are talking about the shuddering. A prior version of TSB-NA-355 DID require that the symptom be verified prior to doing anything, however, a subsequent revision removed that requirement. Read it for yourself here: https://static.nhtsa.gov/odi/tsbs/2019/MC-10163890-9999.pdf
Print it out and show it to the dealer, if need be.