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’m a GM person when it comes to cars ( Chev, Olds, Fiero, etc) all of my trucks have been Rangers. If I purchased another truck it would be a Ranger. My wife had a S10 and I had a Ranger at the same time. I didn’t like to drive her S10. The Ranger always seemed to perform better. Few years difference in age, but not enough to make a choice on what felt better to drive.
Are there any satisfied GMC truck owners our there? I have a friend with a 09 or10 Tahoe and he has over 200000 miles on it. Takes very good care of it. He seems to be pretty happy with it. Just wondering. I owned a 2014 GMC Sierra, MDX with 200000 and now this 2016 Yukon. I am really hoping I did not make a mistake. The Check Engine light still has not come back on….almost a week ago. I cannot believe I am hoping for it to return, still running well.
Lenny
2016 GMC Yukon Denali 58000miles.
I had my torque converter changed at 75k miles and the issue came back at 115k . Changed out the fluids to the “new stuff” and it worked for 5k miles and now the issue is back… I am not happy with my 2016 Yukon Denali XL and it’s only because of the transmission issues. The new special warranty won’t even cover me now because I’m over the 120k miles but my vehicle hasn’t gone more than 60k miles without transmission issues. I use my vehicle mainly for road trips and it sucks that I don’t even want to take them anymore because I am in fear the transmission just might stop working and I’m hundreds of miles from home with my family.
did it fix the problem?
All I did was clear the “Check Engine” light. The code I pulled was P0711. Which states Transmission Temp Sensor error. I have not seen the check engine light for almost a week now. Not even sure what’s even wrong. Yukon runs well. Hope this is a non issue.
My po711 code was a bad transmission wiring harness that threw that code 1 day, then off 2 days later(check engine light never came back on, but it still showed up at the dealership nwhen they ran the diagnostic test) they tested the temperature sensor and listed the ohm readings taken from it to verify that it was ok…
Thanks for the info. I’m going to run it by dealer next week and see what they say. I spoke to another guy yesterday with 2016 Escalade with 6.2. He has had a lot of trouble. AC compressor, transmission and interlink just name a few. All I want to do is drive my “Professional Grade” truck and not worry so much. Maybe I have to stop looking on the internet or talking to other owners.
Hello and not all is lost by resetting the “check engine” light and the code P0711. The dealer just told me that the this transmission issue (fluid flush and temp sensor) will be covered under warranty until 120000 miles. That made me feel better since I did just purchase the vehicle at 56000 miles on it. Was worried it would been lit if warranty at 60000.
Lenny
2016 Yukon Denali 58600
Hello, where have you been informed that the trans issue is covered until 120k miles. That is new information for me, and would make me feel a lot better. Any resources to show us?
Did you see or get the TSB number on extending the warranty??? What dealer were you at and location please….
I was speaking with my Service Advisor at Vera GMC in Hollywood Florida. All I did is call and just told me that today. I will find out where he received that information. He just told me this morning.
Lenny
I just reached out to my service advisor at Vera GMC in Hollywood Florida. When he gets back to me I will pass along any information I get. But based on my first conversation with him he said just this Powertrain transmission issue is extended.
Lenny
This will be my last GM product. The bed was aligned crooked from the factory.Dealer didn’t want to fix it and stated that it was done to help air flow. Now the transmission is total crap with a truck that cost 60 K and less than 2000 miles.
Haha. Air flow!
2018 gmc 1500 only 2000 miles with crappy transmission for sale
Dang, only 2000? If I was in a better situation financially, I’d probably consider it.
Well on my home today that infamous Check engine did eventually return. Dealer is getting it first thing tomorrow.
Lenny
Ok so I am at the dealer and they are replacing the transmission sensor and wiring harness also flushing the system. This is all covered under warranty. The special coverage the dealer is using is code N192291660 (July2020). This is good until 2026 or 120000 miles. I hope this helps.
Lenny, that is excellent info! Thanks for posting!
My dealer would not cover entire fluid cost($300) for complete fluid dump of entire unit and a new filter…
I am now in the same boat. A new 2018 6.2 with the 8-speed. Mostly problem free in just over a hear and a half. I had no complaints of shudder or shifting problem until recently at about 24,400 miles. All of a sudden the shudder started on a saturday. The next day, shudder and extremely hard shifts. Hard as in me sitting in a drive through and the truck would not move while I was on the gas. Hard as in not being able to safely pull out into oncoming traffic. My truck went into the the shop on August 25. Still there as of Sept 9. The flush did not resolve the problem, so a valve body was ordered. Rather, the valve body was back-ordered. I am told i should have it back Sept 10 maybe. That is if the valve body resolved the problem. I really do not want to start over with payments in the time of Covid, but i am very concerned at this point. I dont want to be stranded with my daughter or on a road trip i have coming up. Are the 10-speed in the 2020 models any better?
I’ve seen multiple perceptions of the 10 speeds, just as I have for the 8 speeds. I’m curious as to how many vehicles were produced with an 8 speed vs how many customers experienced issues, whether it be once, or repeatedly. I’m not sure, however there are plenty of units out there that don’t have any issue at all. Let’s say they have a million units/ application of the 8 speed, and only 10,000 have the issues, that’s still a pretty small amount. It’s inconvenient, however Lenny have everyone some good news today. Will every dealer follow that? Of course not, there’s probably quite a few that are behind on the latest news. Now for the 10Speed codeveloped with Ford, I’ve seen where Ford has way more issues with their iteration of the transmission. Now, Ford has had their version out longer. To answer your question though, as I started out with, I’m seeing mixed perceptions about that one, however from what I’ve also seen from YouTube/ internet is it’s better than the 8speed. There are no plans to stop production of the 10Speed. Now, what I’ve seen from the internet is they have parts that are scarce because of the shutdowns and a few other variables, so some configurations will not be produced with the 10Speed until further notice. When I can, I’m getting either generation of truck. It’s all up to you though, and your judgment.
I’d stay away from the 10 spd there having issues, just too much technology and from what im hearing it’s going to be discontinued. Besides its going on almost 6 years and they have no fix for the 8spd enough said.
I’ve mentioned this before but I’ve always been a Chevy/GM guy but having 3 GM cars at the same time with 8 speed trans problems really pi$$ed me off. I traded the Silverado for a 2020 Ram in April and never looked back. That transmission shifts smoother than my Silverado ever did.
Sorry for your frustrations. The same problems happened to me. Shuddering, hard shifts, throttle delay while pulling into traffic… I finally dumped my Colorado last week. I’ll never buy GM again after this debacle. The 10 speeds are garbage too. I’d look elsewhere. GM does not care about taking care of their customers.