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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I have a 2017 GMC Canyon. Shuttering prior to taking it to GM dealer to get fixed. Been reading and looking online about issue. Took to GM dealer, they replaced Transmission fluid with Mobile 1. Now problem seems to be fixed.
Mobile 1 LV ATF HP fluid seems to have fixed my issue too.
I see an easy fix, by truck with 6 speed trany. I have late model 2018 with 24000 and just started shudder. Never heard of it. Daughter has early model 2018 with 30,000 plus and has had no issues. Seems like buying with 6 speed is the solution.
Having a 6 speed is not necessarily the fix. I had 2014 Silverado with a terrible 1-2 and 2-1 clunk that Chevy couldn’t fix. Final diagnosis? It’s normal. My 2018 Cadillac with a very bad part throttle hesitation from a stop or roll has had the triple flush and has been reprogrammed and the final diagnosis? It’s normal. GM has taken a decades proven part to an automobile and screwed it up royally.
Neighbor has 231000 on Chev 1500 used only pulling construction trailer….just had it rebuilt….my wife’s 2016 Cadillac with 6spd.has had no problems at all..Before getting a 17 GMC 8sp I had 2011 GMC with 6spd….shifted normal to 90000 miles
2017 1500 WT in construction fleet. Constantly abused, and pulling things constantly, rebuilt at 70,000. Our company made us drive it at the first sign of failure so it made it worse, could’ve been saved according to dealer transmission tech. I would buy any of these trucks any day.
You wouldn’t have wanted to drive it if it shuttered constantly on the highway.
Correct. Seems rare though, out of all units produced. If it was bad, my service advisor probably wouldn’t own a Canyon and Yukon.
Maybe GM should start analyzing some high mileage no-problem vehicles to see what they have that the problem transmissions don’t.
It’s interesting that as many that have issues there’s just as many that don’t. Seems to be happening sporadically and also i have many friends that owned 2014 up and below and never experienced any issues. They all say they’d never own anything else. Feel bad for all that have issues that GM is sweeping them under a rug with a bandaid fix.
Ive had two 5.3s an 07,18 ZERO problems in 13 years.I mean literally never had an issue,not one.Bought a 2020 6.2 10 speed in the shop within 5 weeks.
I just got my 2018 GMC Canyon and it does this shuddering and harsh frequently more when i get into a stop it jumps from 3rd to 1st it’s scary that my new truck is about to break down on me like that. I don’t know what to do now
“if there is shuttering going on; it’s the assemblers to blame 4 building the transmissions 2 fast”! By not surface-flushing each clutch-plate-fully!” If it’s not shifting fully: it’s the ECM combined w/the sensors that follow w/how a person presses the peddle to activate the machine between the frame rails! it also could be FAULTY WIRES during assembly! “THATS BRAND ISSUES”!
So, Cadillac had my 2017 CTS 3.6 from 12-2-19 through 1-13-2020. I had the chugging problem and surging problem with my car from day one. Finally, after 3 years and multiple trips to the dealer Cadillac finally did the right thing and replaced the torque converter. I had been asking for this since the beginning but they have a “process they have to through. The car now drives and shifts quickly and smoothly with no surging or chugging. On a side note, another issue I had from day one was under heavy acceleration the cabin would fill with a strong sulfur smell. While they had my car, for over 5 weeks, they also replaced the seals and gaskets in the exhaust system. Now, no smell.
Anthony, can you update us? It’s 10 months since your update. Has the torque converter replacement solved the problem?
I didn’t have the TQ replaced other than a few clunking low speed shifts it’s fine no shutter ever. I replaced fluid at 2000 kms with Amsoil and had no issues after that. Trifecta tune helped some
I have an 2018 GMC 1500 6.2 with an eight speed, 10,000 miles.
Have experienced the similar transmission traits.
Just had the latest trans flush.
Still have some similar problems between 1st and second and sometimes a clunk while going in reverse.
So apparently the trans flush is not the total answer.
So they continued installing eight speed transmissions knowing there was a problem.
Doesn’t that sound like fraud?
No! It sounds like “[everyone(brand names included)” Everyone depends on oil 2 fix MECHANICAL issues! When in FACT it’s a COMBINATION of mechanical/ELECTRICAL design & manufacturer issues!
Had the transmission fluid swap and it seemed to fix the problem. Only problem was it only lasted for 50 miles and then it went back to hard down and up shifts.
Isn’t there a 200 mile period of driving before determining outcome? Will the transmission “re-learn” things after this service? (I don’t know)
APPARENTLY GM is 2 cheap to install a “learning” CPU 2 every automobile: by Emoto’s thought?!
June 10, 2017
Harsh shifting conditions and delayed garage shift engagements may be noticed on some 2017 Colorado, Canyon, Express, Savana; 2016-2017 ATS, CT6, CTS, Camaro; 2015 – 2017 Escalade, Silverado, Sierra, Yukon Denali, and Corvette models equipped with the 8L45 or 8L90 automatic transmission (RPOs M5N, M5T, M5U, M5X). The harsh shift conditions may be caused by one or more clutch fill times not completely learned in the Transmission Control Module (TCM).
DTCs and Updated Calibrations
As a starting point for diagnosing all 8L45/8L90 transmission shift conditions, check for DTCs in all modules and address the causes for setting the DTCs. Also check for any available ECM/TCM calibration updates.
Refer to the following bulletins for additional information:
16-NA-411 – 2015-2016 models equipped with the 6.2L engine (RPO L86) engine and the 8L90 transmission
9/13/2017 2015 – 2017 Corvette: GM TechLink: Diagnostic Tips for Harsh Shifting Transmission Conditions – Print View
http://www.corvetteactioncenter.com/…rint-1380.html
16-NA-412 – 2015-2016 models equipped with the 5.3L engine (RPO L83) engine and the 8L90 transmission
16-NA-404 – 2017 models
Test Drive with GDS2
A test drive of the vehicle should be completed in order to attempt to duplicate the concern. Use GDS2 to capture a session log of the event and bookmark when the shift concern is identified. Review the GDS2 session log to identify which shift(s) are occurring at each bookmark.
Refer to the following bulletins for additional information:
14-07-30-001: Information on Transmission Adaptive Functions and Correcting Low Mileage Harsh Shifts, Slips, or Flares – 2015 Corvette
16-NA-411, 16-NA-412 and 16-NA-019: Updating ECM/TCM Calibrations – 2015 models other than Corvette
16-NA-019: Information on Transmission Adaptive Functions and Correcting Low Mileage Harsh Shifts, Slips, or Flares – 2016-2017 models
These bulletins are based on the following criteria:
2015 models with 7,500 miles (12,000 km) or less since the vehicle in-service date, TCM calibration update or the Service Fast Learn (SFL) procedure being performed
2016 models with 5,000 miles (8,000 km) or less since the vehicle in-service date, TCM calibration update or the SFL procedure being performed
2017 models with 2,500 miles (4,000 km) or less since the vehicle in-service date, TCM calibration update or the SFL procedure being performed
Transmission, valve body or TCM replacement requires a Service Fast Learn procedure using a scan tool to be performed in order for the TCM to learn individual clutch apply pressures. If the TCM calibration has been updated, a Service Fast Learn procedure is required on vehicles with any mileage accumulation.
Clutch Drive Learn Procedure
Based on the bookmarks placed in the GDS2 session, complete the Clutch Drive Learn procedure for the suspect clutch. The Clutch Drive Learn procedure should only be performed on smooth, level roads and may take 45 minutes or more.
Completion of the Service Fast Learn procedure will reset all shift adapts and may require the entire transmission Clutch Drive Learn procedure for each clutch to be completed.
After completing the procedure, the vehicle should be allowed to cool down for eight or more hours and then test driven again to ensure the cold shift quality is acceptable.
Refer to the following bulletins for more information:
16-NA-361: Transmission Harsh 1-2 Shift Upon First Start Up/Shift of the Day Under Light Throttle
16-NA-213: Diagnostic Tips for Harsh Shifts after Mileage Accumulation without Previous Transmission
Repairs and/or Calibration Updates – Transmissions built between July 1, 2015 and September 14, 2015.
Garage Shifts
Refer to the following bulletins for more information:
16-NA-014: Delayed Engagement After Sitting With Engine Off. Torque Converter Fluid Drain Back – 2015-2016 models
16-NA-364: Delayed Engagement After Sitting With Engine Off, Clutch Slow to Fill – 2015-2017 models
Has anyone had all the TSB fixes performed? If so, what was the result? It appears my dealer is in the process of doing this and I’m wondering if there is a positive result. I have had the transmission update and learning reset, fluid changed, the shifts re-learned and now I’m having a solenoid and the TCM replaced. I would like to know if someone has had all the TSB fixes done and still has issues. I’ve been pursuing this issue since June 25, 2019 and it’s getting old fast. I still don’t think that the fixes being done will address the delayed engagement I’m having on cold starts.
Just had the valve body and tcm replaced, along with more new oil. The shifting is better overall, but cold shifting is still poor. One new thing that I experienced was the transmission feeling like it was locking up while I was slowing down to a stop from about 30 km/hr. It shook the truck 3 times and felt as if the wheels were locking up.
Glad someone else is experiencing the same thing. I slowest hit someone because of that.
Just had the valve body and tcm replaced, along with more new oil for my 17 Silverado 5.3l 8 speed turck. The shifting is better overall, but cold shifting is still poor. One new thing that I experienced was the transmission feeling like it was locking up while I was slowing down to a stop from about 30 km/hr. It shook the truck 3 times and felt as if the wheels were locking up.
can you email this to me????
This needs to cover the 2019 Silverado. I have this problem on mine with only 400 miles.
“If all Silverado’s are having transmission issues; Then i will not bother having interest to buy a 2020 model!
Drove 22 miles to dealership. Shuttered 38 times. They stated the TBS on the ticket. Changed fluid under warranty. No charge of course. Told me to come back if it did not fix it. Also stated it would take 400 miles to fully take effect. Drove 30 miles after change, did not shutter even one time. Hard to believe the fluid would immediately fix it. Appears it did. Fingers crossed. 2015 yukon with 37000 miles. Have a 100,000 mile 5 year powertrain warranty. Have a full year left. I think they changed the warranty sometime after 2015 to 60000. Was that because of this problem?
I had the fluid change on July 25, 2019 and my hard shifting has not changed. The dealer is even stumped because they felt that the 18-NA 355 TSB would address the shifting issues. I also have surging when shifting from park to reverse or park to drive. The truck likes to take off on me sometimes. I nearly shot into traffic the other day while turning out of a parking spot. To me, my issues have become a matter of safety.
Look at my post above with TSBs that address hard shifting.
So you’re suggesting that I go in there with this list and tell them how to do their jobs? Shouldn’t the dealer know about these fixes?
2018 6.2 Silverado – Hard shifts since day 1 (new). Got the shudder real bad around 8500 and got it flushed as the TSB says at 10k. Shudder seems mostly gone for now (400 miles later) but shifts are still very confused and hard. I have the rough jolt when coasting and reapplying throttle at city speeds and overall drives like crap. The loaner 6 speed felt great but this thing is a 60k farm tractor. I’ll be back to dealer soon…
If all buyer’s drive their trucks like their in a ba-ja race in traffic; your transmission suffers! The transmission & the hardware that makes it move! If you’d drive your truck like cruising in a park; you would save wear & tear! “i say this because the folks who drive their automobiles around me in the city i reside in like each stop-light is a 1/4 mile start” That get’s the attention of your local police!
I don’t disagree, but, that has nothing to do with the subject at hand.
I don’t feel that this comment addresses the known issues. I don’t drive like I’m in a race and actually I find that if I were to accelerate hard, the shifting is better!
I’m sorry but this is absolutely irrelevant to the entire thread. If you note the comments, we have the worst issues at low speeds. Also, I’ve had these issues since itbhad 4 miles on the odometer. No one is racing here and it’s not the cause of our issues.
Actually i was talking about ALL the transmission’s GM makes; not just the 8 speed! it depends on the events @ hand when driving that dictate how you respond w/your foot! // the way i’m answering is based on because this is a public forum! “like the old saying goes: U pay for what you get from the machined parts provided for your dollar=$”!
You are talking out of your A$$. For as many people that are having problems with their GM vehicles you are of the opinion that they all abuse their vehicles? Bull$—t.
I drive mine like grandpa, and the tranny had problems from day one. Took it in and was told they couldn’t duplicate. Now at 29000 miles it’s bad. Very bad. Appointment next week for it’s first attempt at TSB fix doing the flush. My tranny is in no way affected by how it’s driven. This is 100% a build issue from the factory. (2018 Silverado LTZ)
2016 GMC 6.2 25000 miles on mine. I have had all of this done including replacing the torque converter. This is a temporary solution. Got in it last week put it into gear and it wouldn’t move. Took approximately 5 minutes with the truck running before it would move. The shifting and shuttering is gradually becoming like it was before the fix.
This sucks. I have a 2017 6.2 Sierra with 18,000 miles on it. Had a flush done a few months ago. Temporarily fixed the shudder. Then last week they replaced the torque converter. Smooth as butter at the moment. I don’t expect it to last though.
i had the shuttering in my 2015 vette at about 9400 miles,,, took it to the dealer, they said since i drove it three yrs, and had very low mileage, they would first re program the computer or whatever , so it would recognize the i drove low miles..
well they reprogramed it and it probably was worse,,,
the service man said if the reprograming didn’t work, they would have to go another direction,, he also gave me a gm bulletion bout the shuttering,,so they were familiar with this problem tranny,,, so, i traded the vette for a 2019 thinking that gm has solved the problem , now iread that no, they did not,,there should be a lemon law for this situation,, shame on gm,, i called them and told them i was a lifetime chevy owner, but i’d never buy another no matter what tranny was in it… sad, just plain sad that the govt hasn’t stepped in ,and too k care of all the buyers of this disgusting transm.
After reading this, I called my local GMC dealer to schedule my fluids flush. They told me that my 2017 Sierra was not part of the TSB. They told me to wait it out because the Cadillac’s and Canyons are on the list but none of the Sierras. I’m pretty upset with GM even more because of this. I have 58,800 miles on my truck and the warranty expires at 60k.
I just got my 2017 Sierra back from the dealer yesterday. They put a new torque converter in it at no charge. Hopefully this fixes my issue.
How did this work out for you after gettin the new TC ?
I have a 2015 Corvette and it has be back several times for this condition. Nothing seems to work. I’ve had a new torque converter installed and new fluid changed and still shuttering . Not fun to drive. This car is not cheap. I’ve worked for GM for 31 years and am very disappointed with the non concern from the company to get this problem fixed. How am I going to sell this car like this? I have asked the dealer to ask you for a new transmission. I want to drive this car on some long trips but it very annoying to me to drive.
“As of August 7th, GM dealers should also be flushing all potentially affected new vehicles on the lot.” Where is this mandated”? I called my service department and said they know nothing about this. Apparently one has to wait until they have an issue before the fluid is changed?
I have a new unit built in Dec of ’18, so do I have a “ticking time bomb?” Or do I bite the bullet and pay to have it swapped out preemptively?
I had my 2019 Chevy Colorado in for this transmission service on Friday, and it was done on Monday. No more “shuddering” or hard shifting. Apparently the Mobil 1 fluid works.
i have had this service done 1300 miles and my trans is starting to be hesitant and shudder at 4700 miles (2 months)
going back for the third time. proceeding with attorney to lemon it.
What year? 2019? Is it a 5.3 with the 8 speed? Thanks
If it’s a stick-shift; it’s the pressure of the clutch that could be sensitive! (if the years are between: 2015-2019)
Mine is 19 w’ 2.7L either way 8-speed sucks. First new vehicle and the worse buying and ownership exp. ever. Always bought a gm truck and as soon as this one gets lemoned im done with them.
So far just a very jerky (for lack of a better term )1 to 2 low throttle especially cold. I was going to bring up the fluid change with dealer on next service. Is that swap typically done under warranty or do owners pick up cost?
As far as i can remember from 25-30 years back to present; Nearly all auto’s when ran “(cold)”; the lube has not had the chance to move from the pan w/in the 1st 30-45 seconds of starting it!! Research it for yourself to clarify!
Had a loaner from dealer same year, same tranny, without the same issue.
I haven’t found that to be the case in other vehicles I’ve owned over the past 20 years.
Dude, my Colorado is the only vehicle I’ve ever owned that I need to warm up to avoid transmission jerking…. in the SUMMER. That is not normal. This transmission is garbage, stop making excuses for it, “Chevy Enthusiast”.
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I purchased an off lease 2019 Colorado LT with approx. 16,000 miles. Shortly thereafter I noticed an unusual vibration with the shudder at lower speeds going up or down an incline. I called the local GM dealership who were very familiar with the problem, did a road test, informed me that it failed and they replaced the transmission fluid and indicated the did some adjustments. They requested I drive it for 200 miles and if problems persist to get back with the. Initially it seemed better however around 400 miles after the fluid change I experienced a strong “clunk” while approaching a traffic light, not stopping then accelerating off. I observed the slow speed shutter then at various speeds. I took it back to the dealer who checked it out and said they could find no problems and attributed it to a possible spark knock and recommend only use top tier fuel of which I’ve been using since I purchased the truck. Still have the symptoms.