Raced a 16 Silverado 2500hd-6.0...LOST

Discussion in 'Heavy Duty' started by SHOOT2KILL, Dec 26, 2016.

  1. drittal

    drittal Senior Member

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    It wasn't TFL that said the 8sp wasn't going in the HD. They relayed what Ram rep told them. It doesn't change the fact that there is a transmission used in HD trucks with better gear spread. I have to believe in both cases it is a financial decision not to use either. The Aisin just for the premium and the 90 because according to Ram it isn't up the the rigors of a HD without redesign of at least the parking prawl and subsequently the entire case


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  2. drittal

    drittal Senior Member

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    https://www.motor.com/newsletters/20121010/WebFiles/MMM_ZF_8HP_Tranny.pdf

    So in 2012 Chrysler posts about the new 8sp including the 90 and put in print they won't replace HD transmissions. This is before the 6.4l even. Going on 5 yrs and still no use in the HD line even after developing the 6.4l and having to develop the gear hold programming because of the gear ratios of the 66rfe.

    I have to wonder if the downfall of the ZF8 in the HD doesn't revolve around the electronic shift. We have all at one time or another had a vehicle on an incline and it clunked shifting out of park. Maybe the electronics are not strong enough to reliably shift out of park for vehicles at the weights of HD line, including the gas models.


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    Last edited: Jan 8, 2017
  3. yoda

    yoda Senior Member

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    If you go back and read what I wrote, I never said the 45RFE and 66/68RFE were the same, I said they were the same design,I was told this was ludicrous and silly.
    I stand by that statement.
    I think anyone who has both apart would agree with me
     
  4. yoda

    yoda Senior Member

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    Not sure who Brandon is, but anytime the Engine is running there is a clutch applied
     
  5. theviking

    theviking Senior Member

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    I should have stated no holding clutch is applied per the chart. Basically what Brandon was stating is that this is the strongest configuration for a dyno pull. Obviously my overall understanding of an auto trans is limited. So out of curiosity, which clutches are engaged on the 66RFE when in 4th?
     
  6. yoda

    yoda Senior Member

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    OK understood. Makes sense, with no holding clutches applied, the power also goes straight through and doesn't use or put stress on any planetaries.
    UD/OD, in 4th on the 66. same as the 68RFE in your chart above.
     
  7. drittal

    drittal Senior Member

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    If you go back and read what I wrote I never quoted you as saying that. I could be wrong (probably) but from what I have read about the 66 is it is basically Ram taking the gears from the 68 and making them work in the 545 case but with 68 output shaft and extension housing. Thus my short statement of the 66 is basically a 68 stuffed in a 545 case. Sure, there are differences between the them, but the short answer is what I wrote.


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  8. yoda

    yoda Senior Member

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    :)
     

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