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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Certain 2020 10 speeds have been identified by GMs engineers as having a faulty valve body.Im not convinced thats the issue,but time will tell.They are redesigning the valve bodys(mine included at 786 miles)Until than i have no truck AND full payments.GM will not reimburse until the problem is resolved.EVEN so they only offer “up to” 50% reimbursement.It could be 6 months until i have my truck back.GOOD Luck all,use my situation as a determining factor and act accordingly…..
Am I reading this correctly? You have a vehicle under warranty and a recall by GM caused you not to have use of your vehicle for six months and they still expect you to make payments and pay half of the repairs. If this is correct how long do GM plan to stay in business with this type of customer treatment?
They are handling cost of repairs.HOWEVER,they will only reimburse my payments UP TOO 50%,After they figure out how to design,engineer,manufacture and distribute an entirely new part.Good thing i did not have any plans for the entire summer or fall…
They are handling cost of repairs.HOWEVER,they will only reimburse my payments UP TOO 50%,After they figure out how to design,engineer,manufacture and distribute an entirely new part.Good thing i did not have any plans for the entire summer or fall…
My 2019 Canyon sat in the dealership for 94 consecutive days last year. I just happened to drop it off for service for the shuddering of the transmission, non functioning AC, and a whining noise heard when applying the gas. The whining noise was due to an out of the gate faulty pinion gear. There was no replacement to be found on the planet, so the only option was for a complete rear-end assembly replacement, which GM refused to send the dealership – until my BBB case letter arrived at their main office.
GM sent me a check that covered the three payments I made while my truck was in their possession. The service manager also got her District Manager to tag on an extended 5-year warranty.
My truck is hard shifting again from 1st to 2nd and 2nd to 1st, as well as, any slow progression in speed causes my truck to shudder once again, feeling as if I am going up the initial climb on a rollercoaster (the jerking effect).
Service manager is waiting for another truck to come for me to use as a loaner so they can install a torque converter. Two trans flushes have already been performed. Oh yeah, my AC still freezes up after 10 -20 min of driving time. It has been reprogrammed 4 times, this time for the Gulf Coast settings, and I live in NC. This makes 1.5 years I have not had fully functional AC. To top that off, my ambient temperature sensor has failed again as of today, 4 times total now. It reads 79 and it is 94 degrees outside.
94 days wow that sounds like lemon law to me.
I have a 2019 Silverado 8 speed. I have the TC shudder the hard downshifts and the delay from R to D. Shudder is getting to the point it is constant at 1300 RPM. Been back to dealer numerous times, got the flush right away, THEN, working normal, tried to blame the tires. Road Force Balance, no change. Then it was the DFM shutting down cylinders, so acting as expected. I could see if this was something that was just a few, but reading the thread for close to 8 months I can see it is very wide spread and more common than not. GM continues to ignore. And now to hear the 10 speed has issues. How can you ever justify buying another GM product, when they say too bad to the customer. I am an older person and I bought this truck thinking it would be the last and I could keep it. Now I am faced with a big loss of money to replace.
I just traded my Silverado in on a Ram. My Cadillac with the 8 speed has the trans problems and is next to go. I had the triple flush performed on my 2016 Corvette. I really hope that fix works because i wouldn’t know what to trade the Corvette for. So with exception of the Corvette (for now) I am completely done with GM products.
The triple flush was what an earlier version of the TSB prescribed. However, it was done with the old fluid, so was found to not be an adequate fix. Get your dealer to execute the latest version of the TSB with the new fluid, and you should be all set.
Purchased my 2017 Colorado LT 4×4 with 60k miles and didn’t get it 10 miles without returning it for shudder issues, Dealer did the triple flush and stopped the shudder. I added lube guard platinum for added help. It didn’t fix the horrible shifting problems tho. I spent $710 with TRIFECTA tuning and OMG it’s amazing now!!! Everyone on this forum with issues needs to have this tune installed on their 8l45 trans!! Night and day difference! Gm needs to have trifecta tunes all 8 speed trucks.
Awesome, that company Trifecta is also in Ottawa Canada for Canadian viewers. Just reached out to them, awaiting response. Hopefully this is a fix for the notorious 8 speed as it’s a cost out of the customers pockets in some cases that GM should be paying for its ridiculous.
Trifecta will reply first thing tomorrow morning. Once you get the obd2 cord from them and send them back the info they need you’ll have your new tune in 2hrs. I got my cord delivered 5pm, sent back info at 6pm and they emailed me new tune by 7:30 pm. Pensacola, fl time zone. Good luck man! You’ll love your truck again!
Is this Trifecta company reputable and do offer a guarantee??
Sounds great! It’s good to have options. It kind of goes in relation to what I’ve read with people putting aftermarket tunes on their vehicles, with it helping. I think it’ll come back that AFM, and now DFM is a culprit in all of this as well. It also goes to why a lot don’t have the symptoms after they install a Diablo AFM disabler. I’m not sure why AFM exists, however I think we can probably thank the government for such a feature to go from development to using on vehicles. I’m not sure GM will do those kind of tunes though. I believe I’ve read where some dealers will deactivate AFM for you, but most probably won’t. They probably have certain regulations they have to follow, vs what the aftermarket follows.
Trifecta turns AFM off on sport mode but leaves it on on eco mode. I use and like both modes. Just change by leaving cruise armed for eco mode.
I would advise that you get the new fluid. The triple flush version of the TSB used the old fluid which can absorb moisture and cause problems.
Every dealer i call tells me different price and procedure. Why i went to a tranny shop that the owners father who started the business in the 80’s owns colorado that had the issue too. One dealer told me one flush. One told be two flush. Another said drop pan. One said three flushes. And i bought the truck with 123k last year. Has 130k now and fluid was clean. So not sure if previous owner did the flush. Just lnow still not right.
I’ve also looked at their product and sent a message enquiring as to what it would do for my ride…mine is out of warranty so spending $500 is cheaper than a new tranny…
What about the 6spd colorado? Mine does it. And fluid done at tranny shop and shudder and downshift going down hills is worse. The shop said my downshift is actually dangerous its drops like 3 or 4 gears instantly.
Anybody know what’s going on with the Class Action lawsuit?
2015 Silverado Z71 LTZ (72,000 miles)
Took a lengthy trip over the 4th of July weekend and noticed the shudder increasingly got worse as I drove. It had occurred before, but it was rare and only really noticeable during cruise control use. I took it to the dealership and they’re doing the Mobile 1 flush. I will post a follow up once I get the truck back. Additionally, my truck does shift hard occasionally while driving, but more noticeable when going from Park to Reverse/Drive or Reverse to Drive (visa/versa). I’ve given up with the dealer trying to resolve that particular issue as they say, “IT’S NORMAL”. I am really hoping that this flush works or I may unload this truck! I doubt I’d ever purchase another Chevrolet after this experience.
Dropped my 17 Sierra off at the dealership this morning (shudder and hard shifting) and just got a call saying the new fluid would fix the shudder but not the hard shifting because that is being caused by a bad transmission temp sensor. Anyone else been told this? They want $1,300 total — and what infuriated me is I took it in twice while under warranty (10k out of warranty now) and both times was told everything was fine. May be time to walk away from GM.
Ok so I’ve been there done that with my 2016 Denali XL first let me say (by reading on this forum) GO to another dealership and compare prices bc apparently they all differ. Secondly same as you I took it in several times but only after warranty did they suggest fluid change $700. I was also told it was mainly on vehicles in Texas and Florida due to humidity. Sounded suspect but whatever. Lasted one year. Then same problems now it’s the wiring harness $816. Ugh, but do I really want another car note ok fix it. One month later my car wouldn’t drive – RPMs revving, car wouldn’t go over 20mph. Towed it in… after 10 days in shop … and phone calls with engineers in Detroit – oh it’s a bad seal in transmission but since we have had it so long we will split the cost with you – your part is $500. I literally drove my car from GM lot to the Nissan lot and traded it in before I lost any more value. Sickens me American Company will not stand behind their products and loyal customers. Sad to say but I’m done with GM/Chev/Cadillac.
That sounds like BS, never heard of this temp sensor causing issues. If i was to guess the dealership is trying stealership. $1300 UGH. Hearing good things about Trifecta performance and think im going to give it a try if your not dumping it. Check them out
I just had my 15 done for the shudder. They did the fluid flush for $680. I’m going to live with the occasional hard shift for a while longer or trade this thing in. The fluid flush did stop the shudder, but I’m uneasy about whether this will be permanent. Good luck
Damn! They are old me the flush would be between $300 and $400. Told them if they didn’t replace the sensor for free, that will be the last GM I ever own — have already walked away from Dodge, so guess I will go with Toyota — waiting to hear back. If they say no, will tell him to do the fluid only and see if it fixes the hard shift and if they were BSing me.
Update: dealership said GM would cover the sensor and I’m covering the fluid/flush. I’m a happy with that.
According to GM the hard shift from 1 to 2 when cold is normal due to slow clutch fill and I dont think the Trifecta tune will be able to change the clutch fill time.Be a great thing if it did.
Sounds like dealership is full of BS if they put in a sensor and it doesnt change anything they are still going to charge you and you still have shift problem .
Best advice to anyone who owns one is to get the flush using the bosch transflo machine and the newer mobile one. It should be ok for awhile after that unless the torque convertor is toast/glazed. After that sell truck ASAP. This is not one for longevity.
Quick update: 2015 Silverado Z71/LTZ, developed a very frequent shudder and had the fluid flush accomplished. It did work, but the hard shift, for me anyway, is still present. Mine is P to R/D or D/R to R/D. Heavy clunk. I’ve learned to just hold the brake and wait for it. That all being said, I’m not sure if I’m going to hold on to this truck. No that It’s running correctly (somewhat), it may be time to venture to another product. Good luck all!
Anyone with a 2017 Colorado 8L45 needs to have the triple flush (eliminates shudder) and purchase the trifecta tune for $710 for engine/trans recalibration and (REMOVE AFM IN BOTH MODES) and this forum wouldn’t exist. I know it’s kinda expensive but you’ll love your truck again. I feel bad reading these nightmares cause I was there also until a month ago. If you live around Pensacola Florida I’ll swing by and show you how to install it. It basically installs itself, just push a couple buttons..BAM! Fixed! Screw gm for doing this to us! This is what it takes to fix it. You get the vehicle you paid for. Good luck people.
Most people will not even know about that tune let alone pay that much for it. GM wants to fix this but their culture is toxic. They are going back to the bad days when they put out garbage before the US had to bail them out. Needless to say they are fighting hard against all the class actions about this. Ironically, they knew this 8 speed had issues for YEARS before putting it into the truck. They used it in the camaro, vette, Cadillac etc.. Just like Ford thought they would fix their dry dual clutch trans GM thought they would fix this later on. Its over 5 years now. They failed completely.
I’m sitting on the fence about the Trifecta tune wondering if it will work. Had the triple flush done with Amsoil ATF which dealer paid and relearn. It helped but didn’t completely get rid of the lurching and banging at low speed. The tune won’t fix this but helps from what I’ve been told. Also had Range technology on since several years so no AFM
I noticed transmission issues within the last few months. It seems to be getting worse and worse. I decided to Google “2018 GMC Canyon Transmission Issues” and BAM- multiple links came up! I bought it brand new and have about 39K miles. After reading comments- I’m not sure what to do. Call Dealership? Change fluid? Trade it in? I’m sick about this! This truck was my FIRST brand new off the lot vehicle.
Power train warranty is probably 60k — get it into the dealership and raise hell!
Just got my 17 sierra denali back from dealership. took truck there for hard 1-2/2-1 shift plus shuddering. Truck still under warranty so I paid nothing. Temp sensor, two trans harnesses and fluid change was done by dealership. Hard shift is gone but shudder is worse now. Will be returning it to dealership to talk to them and see what can be done.
Well fortunately for you all and unfortunate for me,it seems that GM has identified the issue.Defective valve cover on the tranny.Ill update whenever it is they design amd produce a new one to fix mine,who knows…
Interesting, although makes sense. Where’s the information coming from? Everything they’ve attempted, and everything everyone attempted in the aftermarket with tunes, etc. makes sense as well. I mean if I was complaining about the transmission, and they checked the radio, then I’d be worried. Do you know what series this is for? Obviously it’s for the 8 speeds, but is there more involved like 6, or 10? The 6 seems fine though comparatively. I haven’t driven the 8 or 10 yet though.
My 6 speed 2016 trailboss is identical issues. Why it confuses me the suit is for 8speed only.
Got my 2016 Silverado back 2 weeks ago. Had the Flush and Valve replaced. Fixed the Clunk from 1st to 2nd gear. I have put on just under 600 miles and now I have a pretty noticeable clunk (but no lurching forward) going into 6th gear. Not feeling to confidant that the Valve replacement is the fix. My optimistic side is saying at least when I’m driving at low speeds people cant hear how crappy my transmission sounds. The pessimist in me just wants a Transmission that works. Good Luck Everyone, Stay Safe while GM allegedly tries to find a fix for this.
This is for all of you people who think that GM is doing a “good job” trying to fix their transmission problems. I am looking at this from a different point of view. I purchased a 2017 GMC Sierra 4×4 and loved the truck. I loved everything about it except the transmission problems that it had. My truck listed for $57,400 and I was able to purchase it for $45,000. I kept it for “One Year” before trading it off for a Ford Expedition. During that one year that I had the truck, I had it in the shop multiple times like all of you people have and they never fixed the problem. They would tell me that the vibrations and things that I was having was, “Within Tolerance”. I told them it was not within tolerance because, I can’t tolerate it. Anyway, I got tired of the stupidity of have such an expensive vehicle that has so many problems.
My point is this, I traded my truck off after just under one year because of the transmission problems that I didn’t even cause so, how much money do you think I lost on that vehicle after trading it in that quickly. I can tell you, it was a lot. So, I think that during the class action lawsuit against GM, they should also consider making them pay for people like me that lost money because of their terrible product that they charged me a lot of money for.
Hopefully, some of you can relate to this because you lost money by trading your faulty new vehicle off due to their problems. They should have to pay for their mistakes and not us.
Are they doing a bad job? They aren’t. They are looking at every aspect of the transmission that’ll cause those symptoms. Could they do better? Absolutely, there’s always room for improvement for everyone, and corporations are no different. The way this structure works is, once a vehicle is sold, the engineers continue research when problems come up. When they find something that could potentially remedy an issue, it is put out as a document could a technical service bulletin. That then goes into a database for reference for when dealer technicians, and other service personnel get a vehicle in for service. If the technician cannot find anything from engineering, they say that everything is fine. There are exceptions to that rule. Engineering supposedly takes things from the field as well, which means taking technician opinions into consideration. If a problem matches, the work gets done, if it’s under warranty, or recall, you leave happy. Some parts they can just replace under warranty no problem, some others they have to have engineering input. When I worked at a Toyota dealer, a guy complained about rust spots on his frame on his new Tundra, and the service director looked at it and said it was normal, sounds a little odd coming from a brand that had frame issues. All the manufacturer’s follow the same pattern as I described. It’s definitely a frustrating experience, however they’ve had bulletins come from the engineers from GM for this issue. For why it’s taking so long, I honestly have no idea, I’m not there in the engineering department. I work in construction making $14 an hour, but have some knowledge of how this process works.
We can put a man on the moon 50+ years ago, GM can switch gears (no pun intended) in a matter of weeks to make ventilators but they can’t figure out why a transmission shutters, shifts hard, hesitates etc? They either aren’t trying hard enough or they really don’t give a crap about it or think that the problem will take care of itself due to attrition if they can stall long enough. Any way that I look at it it’s bad business and they are going to permanently lose customers big time.
2017 Chevy express 52300 miles. Had the shutter at low rpms. Sounded like I was going over the ripples on the side of the high way. I wasn’t home when it started making the noise so I had to drive it 150 miles back. All covered under warranty. Torque converter needed to be replaced. They didn’t put Mobil 1 in for fluid but the guy said there was a lot of debris. Don’t know why so many vehicles are having tranny trouble so early nowadays