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    Thread: Learn me some newer GM Truck Automatics (6L80/8L90/10L80)

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    1. Member tampaSi's Avatar
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      06-29-2020 05:28 PM #1
      All,

      Currently going through a round of "future planning" and the wife has her eye on a GM full-sizer to pull road trip and future kid hauling duties. This puts us in a 2015+ Tahoe or Yukon (Suburban/Yukon XL are too big, Escalade too expensive + I hate CUE), and I'm lobbying for the Yukon Denali since it's got the 6.2L. Back in my car reviewing days, I drove all manner of new K2XX platform GM trucks (Tahoe, Suburban, Escalade, Silverado, Sierra) but oddly never a Yukon Denali; I always came away impressed with these trucks, and from what I can tell they appear to be holding up nicely. The Denali also holds its value really well, still commanding close to $40K for a 2015 with 50-ish thousand miles.

      That said, I know GM's recent automatic transmissions can be finicky. Based on the limited research I've done, it appears the 2015- Denali came with one of three automatics. Early 2015s had the 6-speed (6L80), mid-cycle 2015s started getting the 8-speed (8L90), and then from 2018-on the Denali has been getting the GM/Ford 10-speed automatic (10L80). A 2018 is probably out of budget anyway, so I'd rather focus on the 6-speed versus the 8-speed.

      Is one of these inherently better than the other? I know more gears is generally better but I've heard some Colorado/Canyon owners on this forum complain about programming/durability issues with the 8-speed, so perhaps the 6-speed is actually the better option if I can find one?

      That said, learn me TCL!


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    2. Senior Member JustinCSVT's Avatar
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      06-29-2020 06:14 PM #2
      Not an expert on GM like I used to be but I know the 8-speed had an issue with hard shifting on the 1-2 shift. Supposedly a flash and fluid change fixes it but I don't know if its a permanent fix.
      2017 VW GTI

    3. Member
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      06-29-2020 07:53 PM #3
      The 8AT in my 2020 5.3L Silverado is the only thing I have a legitimate issue with on the truck. It's good to go 95% of the time, but there's a solid 5% during freeway merging/on-ramps where it feels like the transmission is going to fall out of the damn truck while it downshifts a few gears. Having a ZF8 and DQ500 in the garage with similar sticker prices has made me question how GM has continued to put this ****ty 8AT in their trucks, but it is what it is. It really is 5% of the time.
      2019 RS3 // 2019 SQ5 // 2020 Silverado RST

    4. 06-29-2020 09:22 PM #4
      The 8AT in the 15-18 Denalis is problematic, if you can afford it definitely avoid it. Posts all over the place on GM Trucks forum about rough shifts, hunting, etc. I have a 2019 (10L80) that shifted pretty rough for the first 2500 miles or so, but is has really smoothed out as it has mapped itself to our driving style. I no longer have any complaints, and it always seems to be in the right gear. The gas pedal also has a kickdown switch at the very end of travel, so if you really floor it it'll drop into the lowest gear available, and quickly. In a truck this size, it's ridiculous to go from 60-80 nearly instantly.

      I would highly recommend any 19+ model of the current GM set. You can get the 6.2L in a Tahoe has well, if it has the RST Performance package (NOT the RST Trim package), or the 2020 Premier has the 6.2L as an option. The 5.3L is perfectly capable, but the 6.2L is way more fun, livens up the truck, and brings basically no punishment at the pump.

      Nearly all of the kinks have been worked out in the platform, and you can get a great deal on them since the new ones are just around the corner.

      If you can find on the with ACC and the heads up display, both are features you think you won't use but become requirements after you get used to them.

    5. Member TangoRed's Avatar
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      06-29-2020 09:58 PM #5
      It really sucks that the 8L90 isn’t a great transmission. I’m going to need an additional vehicle next year and the Yukon Denali seems like a good candidate, but the 19+ models are going to be more than I want to spend.
      Quote Originally Posted by Doug Butabi View Post
      And on the tenth day of the two thousand fifteenth year, TCL finds out about rich people.

    6. Member tampaSi's Avatar
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      06-29-2020 10:35 PM #6
      There's a 6AT 2015 Denali close to me, might have to go and drive it. You've all confirmed my suspicions that the 8AT is no good.
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    7. Member fireside's Avatar
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      06-30-2020 07:02 AM #7
      Quote Originally Posted by shimps1 View Post
      The 8AT in the 15-18 Denalis is problematic, if you can afford it definitely avoid it. Posts all over the place on GM Trucks forum about rough shifts, hunting, etc. I have a 2019 (10L80) that shifted pretty rough for the first 2500 miles or so, but is has really smoothed out as it has mapped itself to our driving style. I no longer have any complaints, and it always seems to be in the right gear. The gas pedal also has a kickdown switch at the very end of travel, so if you really floor it it'll drop into the lowest gear available, and quickly. In a truck this size, it's ridiculous to go from 60-80 nearly instantly.

      I would highly recommend any 19+ model of the current GM set. You can get the 6.2L in a Tahoe has well, if it has the RST Performance package (NOT the RST Trim package), or the 2020 Premier has the 6.2L as an option. The 5.3L is perfectly capable, but the 6.2L is way more fun, livens up the truck, and brings basically no punishment at the pump.

      Nearly all of the kinks have been worked out in the platform, and you can get a great deal on them since the new ones are just around the corner.

      If you can find on the with ACC and the heads up display, both are features you think you won't use but become requirements after you get used to them.

      Glad I'm not the only one... I'm currently at 550 miles on my Ford 10R80 and yeah it's definitely a little herky jerky still. Everyone seems to echo your extended break in/map learning time so I'll wait.

      To OP: seems like all of these newer multispeed transmissions are kind of finnicky, with the ZF8 being the shining star. Even then, I've seen the ZF8 slip up here and there in my experience. There is just so much going on.

    8. Member tampaSi's Avatar
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      06-30-2020 02:54 PM #8
      Quote Originally Posted by fireside View Post

      To OP: seems like all of these newer multispeed transmissions are kind of finnicky, with the ZF8 being the shining star. Even then, I've seen the ZF8 slip up here and there in my experience. There is just so much going on.
      Current | Mk7 GTI
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    9. Planters (fasciitis) peanuts. Dang dogg Sold Over Sticker's Avatar
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      06-30-2020 12:08 AM #9
      Quote Originally Posted by JustinCSVT View Post
      Not an expert on GM like I used to be but I know the 8-speed had an issue with hard shifting on the 1-2 shift. Supposedly a flash and fluid change fixes it but I don't know if its a permanent fix.
      My friend is in the middle of this with his ATS-V with the 8L90. Flash, fluid change, and something else. Next step is a replacement under warranty. 38k miles. Clops and bangs the 1-2 shift, slips the 2-3 shift, and binds and makes a clunk and a shudder when the torque converter unlocks.
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    10. Geriatric Member ValveCoverGasket's Avatar
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      06-30-2020 01:32 AM #10
      Quote Originally Posted by Sold Over Sticker View Post
      My friend is in the middle of this with his ATS-V with the 8L90. Flash, fluid change, and something else. Next step is a replacement under warranty. 38k miles. Clops and bangs the 1-2 shift, slips the 2-3 shift, and binds and makes a clunk and a shudder when the torque converter unlocks.
      i think thats the same trans thats in the 8spd gas colorados? everyone seems to hate that transmission and the infamous TC shudder.

      if so, i would pass. sounds like nothing but trouble from the small pickup forums.

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