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Thread: GM 8 speed

  1. #1
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    Default GM 8 speed

    Has anyone experienced hard shifting or a shutter from a 2015 to 2019 GM 8 speed. Mine started yesterday. Was told to bring it in and flush it replace fluid with a new Mobil 1 synthetic.

  2. #2
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    Yes, been in the shop three times.

    First time they fixed a vacuum hose.

    Second time they changed the fluid.

    Third time they changed a temperature sensor.

    It's not as bad, but still shifts hard in 1/2/3......only when first starting, like in a parking lot or something after it's been sitting a while.

  3. #3
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    Default

    Wife’s Tahoe did this twice last week. 2019

  4. #4
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    Oct 2014
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    I have a 2018 Sierra with 34k. It started shuttering last week when between 1500-2000 RPM. I took it in Friday and they put the Mobil 1 in it. It also would shift hard after sitting, from first to second. So far, after some weekend driving, it’s been fine, we shall see. The GM Authority website has some discussion about it.


    Sent from my iPhone using Tapatalk

  5. #5
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    Nov 2012
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    Wife had a new Escalade. Traded it in with 20k miles because a ton of transmission issues.

  6. #6
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    Take it in and your problems will be over when they replace the fluid
    Gettin old is for pussies! AND MY NEW TRUE people say like Capt. Tom >>>>>>>>>/
    "Wow, often imitated but never duplicated. No one can do it like the master. My hat is off to you DRDUCK!"

  7. #7
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    Got the transmission flushed at the Mobile Synthetic put in today. Seemed to be ok on the 15 mile drive home. Let's give it some time and see how it goes.

  8. #8
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    Jan 2020
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    Coosa Valley
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    Fluid has lasted 20k.

    Shuddering stopped completely after new fluid.

    Hard shift still there.

    I try to crank it and let it warm before she leaves when i have the chance. If I'm driving, tow haul button as soon as I sit down and rock on. That 6.2 never leaves me wanting more. I cant imagine that one w/ a charger. Got to be a beast. Build me a perfect non diesel truck, --2500hd, 6.2 supercharged, 10spd, 4x4.
    Double Secret Probation Officer

  9. #9
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    I like the hard shift myself. Love the 8-speed
    Gettin old is for pussies! AND MY NEW TRUE people say like Capt. Tom >>>>>>>>>/
    "Wow, often imitated but never duplicated. No one can do it like the master. My hat is off to you DRDUCK!"

  10. #10
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    Flushing it with Mobile one is supposedly the fix. Add a bottle of limited slip friction modifier and that shudder will be gone.

    Pro tip
    More fuel = more boost!!

  11. #11
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    Thanks Kevin. Question does the dealer over the cost for flush and refill?

  12. #12
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    Quote Originally Posted by Biggie1976 View Post
    Thanks Kevin. Question does the dealer over the cost for flush and refill?
    I did one last week that was fed up with the dealer. The mobile one and the additive fixed the shudder. They should cover it to 60k but they won’t add the limited slip modifier. It’s 9.00, add it afterwards.
    More fuel = more boost!!

  13. #13
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  14. #14
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    Thank you

  15. #15
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    What brand and how much modifier do you add?

  16. #16
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    I use Motorcraft limited slip friction modifier in the 4 oz bottle. Old school tranny guy taught me that trick in my BMW days. If that doesn’t fix the shudder it will be torque converter time.
    More fuel = more boost!!

  17. #17
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    Um, I think he said a bottle
    Gettin old is for pussies! AND MY NEW TRUE people say like Capt. Tom >>>>>>>>>/
    "Wow, often imitated but never duplicated. No one can do it like the master. My hat is off to you DRDUCK!"

  18. #18
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    Um, they sell different size bottles.

  19. #19
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    It’s a GM, get the biggest one they make, you’ll need it.
    Yeah, but do you consider a dog to be a filthy animal? I wouldn't go so far as to call a dog filthy but they're definitely dirty. But, a dog's got personality. Personality goes a long way.


    You might take out a dozen before they drag you from your home and skull fuck you to death. Marsh Chicken 6/21/2013

  20. #20
    Join Date
    Jan 2012
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    Mine will seem to start in 2nd or third when you back out of driveway and then slam into first. Is this the same issue?

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