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GM 8-Speed Transmission Lawsuit Heats Up - Does Yours Shudder?


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.02 Regarding the fluid change there's one thing to consider. Vehicles w/8 spds manufactured after 3/19 come stock with the new Mobil1.....GM didn't substitute an outside supplier brand for their own Dextron just for laughs......there is a reason why the Dextron which is as hydroscopic as ever used in previous trannys going way back now messes up in certain * speed trannys. I have no idea why GM mad a decision for a major flush and fill but could be that certain parts are affected by hydrated Dextron, but could it be because of how affects mating surfaces, degrades components, driving conditions, environmental conditions, changes viscosity affecting servo fill rates, etc.?

 

But whatever the reason according to posts here appears a refill with Mobi1 fluid corrects some but not others.....seems like a major commitment to do a complete flush shipping special equipment for the operation as described in the TSB above..........So..possibly the ones that work were flushed correctly and the tranny suffered no permanent damage operating in the interim on the Dextron and the ones that did not could possibly be because the flush was not done properly or it was done properly and damage not correctable by the change had already occurred or the vehcile was driven improperly and under conditions which caused damage not correctable by a fluid refill.

 

And as far as my first hard 1-2 upshift after an overnight cold is definitely temperature related  ....instead of just zipping out below 32F, idling and warming the tyranny to around 85F first mitigates or eliminates the first hard 1-2 upshift quirk.

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Looks like GM will be putting MQE's in place of the M5U's?  I would expect nothing less as this has been a major problem for them for years.  Anybody who has ever hit the gas in a pinch and their truc

IMHO it is the AFM system that makes most of the 6 or even 8 speed 2014 and up GM trucks shift like crap. I have proven this myself by running my 6 speed around in M5 or using E85 Overall I

This is a bit hyperbolic. 

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On 12/12/2019 at 2:06 AM, Chad2815 said:

Mine shudders and hard downshifts. Been flushed 3 times, right now its better but still there. Hopefully the new Tundra is nice because this is probably my last GM. Not because of this issue because I know stuff breaks, but because of the way they have handled my repairs. Its like pulling teeth to get them to do anything. 

You and me both. I'm sick of all the crap on my 2014 breaking. Had my starter go out twice, brake booster fail, AC compressor went out, bed bounce on the highway, sudden drops in throttle response, shitty gas mileage, lights/buttons on the dash failing, trailer brake sensor warnings go off randomly all year long (with nothing connected), and leaking CV axles. 

 

Unfortunately the Tundra redesign probably isn't coming until fall 2021, and since I don't want a new model year I'll have to wait until the 2022 model drops. If they get a crewmax with a 6.5' bed I'll throw all my money on it.

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yes I have had simular issues  my Yukon Denali had the flush done in Oct 2019 with a valve body change and the problem are back.  One problem i have when vehicle sits for several days in my driveway at first start up when you place vehicle in reverse I dont feel it engaging it kinda slides into gear and then is followed up by poor shifting for the next couple of miles. returned it to dealer they say cant reproduce it and cant fix it.  I am also starting to hear pump whine as i am driving.   has anyone had simular issues

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I have a RST and it does the same thing. Reverse to Drive can be a little harsh so I have to remember to not give much gas until I am sure its operating correctly.  At 17,000 miles it really likes to clunk in to 1st as you are almost to a complete stop. The wife and I were cruising the lake shore looking at some nice lake homes with multiple stop signs so I put the truck in manual shift mode so I could shift to prevent the annoying down shift clunk. It seems to be acting up more frequently.?

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On 1/18/2020 at 4:29 AM, Thomcat said:

.02 Regarding the fluid change there's one thing to consider. Vehicles w/8 spds manufactured after 3/19 come stock with the new Mobil1.....GM didn't substitute an outside supplier brand for their own Dextron just for laughs......there is a reason why the Dextron which is as hydroscopic as ever used in previous trannys going way back now messes up in certain * speed trannys. I have no idea why GM mad a decision for a major flush and fill but could be that certain parts are affected by hydrated Dextron, but could it be because of how affects mating surfaces, degrades components, driving conditions, environmental conditions, changes viscosity affecting servo fill rates, etc.?

 

But whatever the reason according to posts here appears a refill with Mobi1 fluid corrects some but not others.....seems like a major commitment to do a complete flush shipping special equipment for the operation as described in the TSB above..........So..possibly the ones that work were flushed correctly and the tranny suffered no permanent damage operating in the interim on the Dextron and the ones that did not could possibly be because the flush was not done properly or it was done properly and damage not correctable by the change had already occurred or the vehcile was driven improperly and under conditions which caused damage not correctable by a fluid refill.

 

And as far as my first hard 1-2 upshift after an overnight cold is definitely temperature related  ....instead of just zipping out below 32F, idling and warming the tyranny to around 85F first mitigates or eliminates the first hard 1-2 upshift quirk.

FYI, there are two different Mobil one trans fluid. a silver label and blue label. I believe the blue is the most updated fluid, that came in the 3/19 trucks. Sadly mine was built in 1/19.

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Just received the new flush talked about here Bulletin No.: 18-NA-355 and so far so good. But this is my 5th time to dealer for the shutter. 2 years ago did a flush worked for a bit, shutter returned. Then new torque converter. Next year new blue label Mobil 1 Synthetic LV ATF HP fluid. We will see.........

The funny thing when I took it back this time the local dealer said it needed new transmission. I said OK. Later that day they said not one transmission to be found in the US so we will rebuild this one. I said OK. The next day they said well our transmission guy left dealership and working somewhere else now so we need to send your truck to our other dealer 20 miles away. I said OK. That dealership called and said we will do our own diagnoses. I said OK. The next day they called and said they had found the Aug 2019 bulletin on the new oil and so far so good after 20 mile test drive. After driving home after picking up I did notice a huge improvement but need to drive 200 miles for the full effect. Fingers crossed. I am only 10k from going out of warranty or 3 months. After reading this forum I am not to sure about this.

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On 6/2/2019 at 2:05 PM, Snoringbear said:

Took my 2015 6.2/8 spd Silverado in for an oil change a couple weeks ago.  While talking to Customer Service Rep I mentioned that my tranny was still shifting hard between 1st to 2nd and vise-versa at low speeds.  And, the three quick-flash reprogram hadn’t fixed anything.  Also stated if they couldn’t come up with a fix I was going to demand a new tranny.  Rep, said that a new tranny might not correct the problem as they have made some swaps and customers still had the problem with the new tranny.  Then, he stated that there was a new ATF out that was giving excellent results.  Said it was Mobil 1 Blue Label.  I said let’s give it a try.  So, long story short, they did the flush per the SB and put in new Blue Label fluid.  Almost immediately I could tell a difference.  And, now that I’ve put about 100 miles on it the shifts are smooth.  Haven’t had a single  hard shift since.  Fingers crossed ?! 

It'll come back.  

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Got rid of my 2015 a month ago for issues with the 8 speed transmission. That was my last newer GM pickup, I've had six different ones over the years and have only had two that I didn't really have any problems with.

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"Got rid of my 2015 a month ago for issues with the 8 speed transmission. That was my last newer GM pickup, I've had six different ones over the years and have only had two that I didn't really have any problems with."

 

So in short, they would usually experience problems along the way? Since you only had two with "flawless" experiences?

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