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attn: what rpm's are ya'll runnin with your TH400's

Discussion in 'The Garage' started by 01maroonz71, Feb 26, 2007.

  1. 01maroonz71

    01maroonz71 1/2 ton status

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    basically im wondering around what stock would be at cruising speed on the highway, im going on a 700mile round trip journey at the end of next month and need to know how bad my MPG is gonna be...haha, im not sure what gears i got since i bought the truck as it sits, but with my 38's and my TH400...

    i'm doin 2400RPM at 70mph, which is alot....

    i may look into a gear vendors o/d....somebody locally is selling one....

    anyways, what do ya'll run at???? thankss!!!!

    hopefully some stockers will chime in.
     
  2. Beast388

    Beast388 1/2 ton status

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    A TH400 has a 1:1 final ratio like everything else that doesn't have OD. If you are spinning 2400rpm at 70mph then you have a 3.88:1 ratio according to 4lo.com's calculator. Since that isn't a standard ratio, I'd bet you have 3.73:1 gears. You can cruise at 70 all day long spinning only 2400rpms.

    Count your blessings.....at 70mph. I'm spinning 3500rpms.:doah: :D
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Here's mine:

    235/85r16s(just under 32" tall) with 4.10s = 2900 RPMS at 60 MPH
     
  4. 01maroonz71

    01maroonz71 1/2 ton status

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    damn, so maybe my mpg won't be so bad at all.....hmmm....wish i had more low end grunt though...i geuss i only get one or the other
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I'd gladly trade a little "low end grunt" for some lower top-end RPMs.......:rotfl:
     
  6. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    Ideal, just getting into the sweet spot on the torque band.
     
  7. 79k20350

    79k20350 3/4 ton status

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    x2 2400 rpms is the sweet spot. great mileage/ power (well not great, but as good as it gets:p:)
     
  8. 01maroonz71

    01maroonz71 1/2 ton status

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    10-4...i think im prolly gonn leave the gears then...since i have a pretty wild cam that give me awesome low end power...i used 4hi the other day and it did awesome....no need for 4lo at all....i geuss i do kinda have the best of both worlds. well, ill let ya'll know what my mileage will be...hopefully 12or better. i have noticed more MPG since my e-fan install....which is o.k. with me.
     
  9. Russ

    Russ 1/2 ton status

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    235/85r16's with 4.56's and 489 engine in my dually. According to my engine scanner I am doing 3100 RPMS at 60 MPH and I get a whopping 3-4 mpg on a good day.
     
  10. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    :dunno:

    Wild cams are generally the ones that give top-end power at the expense of low-end torque.

    What sort of cam specs are you talking about here??
     
  11. 01maroonz71

    01maroonz71 1/2 ton status

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    well, greg...i must clear this up, im not sure the specs on the cam, but it lopes something fierce, and i've got plenty of power from about 1500 up, so i call that "low end" maybe that's mid range or so...but where i go muddin, it does me fine. wish i new the specs on the cam, but i don't. just know that it sounds AMAZING!!!! haha :)
     

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