How fast will my truck run?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by JSmitty, Mar 30, 2009.

  1. JSmitty

    JSmitty Light Load Member

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    I don't have the slightest clue how fast my truck will run. All I know is it's balls to the wall if I want it to, but speedo only goes to 85, so here are some details, and maybe someone can clue me in what top speed might be. Or, is there a site out there that can give me all the details?


    18 speed
    Max RPM set to 2100
    355 rears (Peterbilt), atleast I'm thinking 355's. It's 35* something
    24.5 lo-pro's


    70 mph and I'm sitting around 1400 rpm

    What yall think?
     
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  3. lostNfound

    lostNfound Road Train Member

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  4. JSmitty

    JSmitty Light Load Member

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    Um....my speedo buries at 85 mph, which about 1700......that leaves me 400 rpm to go.


    Guess I need to find out the ratio of the tranny then. Tell you waht, I know it's gotta be around 120 or more, because it actually scares the hell outta me, lol
     
  5. HISPEED428

    HISPEED428 Light Load Member

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    100mph + or - a few if U got .73 OD in the big hole.
     
  6. HISPEED428

    HISPEED428 Light Load Member

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    No way with it goes 120mph with that ratio.
     
  7. lostNfound

    lostNfound Road Train Member

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    Sounds like you might have something higher (numerically lower) than 3.55 ... 3.25 maybe (max 106 mph)?
     
  8. JSmitty

    JSmitty Light Load Member

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    Maybe it just feels faster, lol. I never do it, but I have had it there a time or 2, just to see what it would do, lol
     
  9. lostNfound

    lostNfound Road Train Member

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    Engine RPM x 60 / (Axle Ratio x Tire Revolutions per Mile x Transmission Ratio) = Top Road Speed (MPH)
     
  10. JSmitty

    JSmitty Light Load Member

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    Cool! Thanks for the formula. Wonder how I go about finding out what ratio the tranny is? Run the numbers on it?
     
  11. HISPEED428

    HISPEED428 Light Load Member

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    2100rpm,0.73 ratio in top gear,2.64 rear ratio,24.5 lo-pro tires gets U 134.87 mph + or - a few.It would probably have a he!! of a time tryin to get out of its own way tho.lol
     
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