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Thread: 8L90 TCC Locks and Unlocks Every Eight Seconds

  1. #21
    Tuner ZeroBoostBuick's Avatar
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    Quote Originally Posted by damnlucky06 View Post
    New fluid just came out, the old formula for the trans fluid was hygroscopic, new fluid works stupid good at resolving the tcc shudder , I'm a dealer trans tech and man I am very skeptical on almost everything GM comes out with , but man the new fluid impressed the hell out of me, have had probably 20 8l90 and 8l45s in with terrible shudders , and the new fluid almost instantly cures it, gm says must be driven 200 miles

    Thanks for the input.
    I've always noticed AMSOIL ATF made mine (and other) transmissions works smoother.
    So I'm not surprised at what you said.

    But give us a little more info about this "new" ATF. What's it called ?? Dexron VII ??? cause I can't find anything about a new GM ATF anywhere.

  2. #22
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    im Looking for a reputable non dealer gm shop in the Bay Area ca (I’m in concord ) to do the flush for me.
    Dealer “couldn’t replicate” for me of course so it’s customer pay.

    I’d rather not pay dealer mark up pay. I need to do a 8l90 and an 8l45

    Sadly I don’t have access to a lift and I’m disabled so getting under the truck for this isn’t on the top of my “want to do lists”

  3. #23
    Advanced Tuner Dr. Nopps's Avatar
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    For what it's worth man, pretty muuch every GM vehicle I've extensively driven seems to do this if you can even feel it most of the time is another thing. You actually gathered quantified data on it, that's cool. Seems like they started controling the auto transmissions differently post 1997-1998 or so and after that they wouldn't like to just stay locked. I was able to get my car to stay mostly locked however by adjusting obviously the lockup points, but also by raising the maximum ammount of allowed convertor lockup increasing engine load just a little basicly matching that same load I would get under light acceleration, allowing the transmission to stay in overdrive, with convertor fully locked without cycling on flat ground and even slight downhill slopes as long I maintain a steady consistent accelerator position.
    Last edited by Dr. Nopps; 02-10-2019 at 12:10 PM.

  4. #24
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    New Bulletin is 18-NA-355 dated 3/1/2019. Bulletin too large to post.

  5. #25
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    Can you link to a sandy blog or elsewhere that might have it?

  6. #26
    Tuner ZeroBoostBuick's Avatar
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    https://gm-techlink.com/?p=11127

    Besides the Mobil-1 Low Viscosity ATF I would think AMSOIL's Signature Series Fuel Efficient ATF could also be used since it's a Low Viscosity ATF as well.
    Last edited by ZeroBoostBuick; 04-30-2019 at 04:19 PM.

  7. #27
    Do you think this would help with 6l80 and 6l90, I have experienced shudder in them, generally when commanding 0 or low slip at moderate loads, slight inclines, towing. the TCC pressure seems to drop back despite what I set the apply ramps, offset or gain to. Ironically I find the feel best if you allow more slip but I'd rather have the TCC lock for longevity and economy.