Stock Rear End Size and Gear Ration in 71 Demon 340

Transmission and Drivetrain Tech

  1. Gibber

    Gibber FABO Gold Member FABO Gold Member

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    Hi,

    Trying to find out what stock rear end size and gear ratio was fitted in 71 Demon 340 with 4 speed.

    Thanks in advance,

    Mark
     
  2. Dana67Dart

    Dana67Dart The parts you don't add don't cause you no trouble FABO Gold Member

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    I would assume an 8 3/4

    As for gear ratio. Look in yoyr factory service manual so e times they list what was stock for a particular application

    Do you have a fender tag or a build sheet?

    There are options that could have been ordered for gear ratio, like a towing package might have a diferent ratio, a limited slip might have another ratio
     
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    • 33IMP

      33IMP Well-Known Member

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      71 340 car would have an 8 3/4.
      As for gear ratio, i would bet on a 3.23 open being the base gear, with 3.55 and 3.91 optional, along with suregrip.
      Happy to be corrected by somebody that knows for sure.
      Easy enough to find out what you have. You'd need a couple pieces of tape, and a floorjack (and jack stands!).
       
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      • dadsbee

        dadsbee FABO Gold Member FABO Gold Member

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        1964dodge440rearaxleandjackparts 009.JPG
         
      • Gibber

        Gibber FABO Gold Member FABO Gold Member

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        Thanks much! It will be going to a friends shop to use his lift for pics of the NOM engine and transmission VIN numbers. I'm planning on offering it for sale in the next month or so. I have the fender tag but haven't looked for the build sheet yet.

        Mark
         
      • Sublime one

        Sublime one 72 Demon FABO Gold Member

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        Mine is 8 3/4 with 355
         
      • Dana67Dart

        Dana67Dart The parts you don't add don't cause you no trouble FABO Gold Member

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        Fender tag might tell you what it is.
         
      • MopaR&D

        MopaR&D Nerd Member

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        If you can't figure out from fender tag or build sheet you could just jack up the rear of the car and spin the wheels, see if both wheels turn the same direction (if yes, you have Sure-Grip) and also count how many times the driveshaft turns with one full rotation of the rear wheels. IIRC 4-speed cars usually came with 3.55 or numerically higher gears, starting ratio with 3.23s is kinda tall with a non-OD A-883.
         
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        • YY1

          YY1 Well-Known Member

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          Dealer data books at hamtramckhistorical should show what the standard and optional rears were depending on other options and packages.
           
        • 33IMP

          33IMP Well-Known Member

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          Agree with mopar r&d. I f were your buyer, i wouldnt give a crap what "stock" is, i would want to know whats in it now.
          Factory info about what might have been in it 50 years ago doesnt mean as much as whats in it now.
           
        • 33IMP

          33IMP Well-Known Member

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          If i buy a car that the fender tag or broadcast says came with a 3.91 sure grip, and i find out its got a 3.23 open, im gonna be pissed.
          You better find out what is there, rather than depend on what was stock 50 years ago.
           
        • 71GSSDemon

          71GSSDemon FABO Gold Member FABO Gold Member

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          Mine is an auto car, but came with 8.75 and 3.91 SG
           
        • Gibber

          Gibber FABO Gold Member FABO Gold Member

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          I’ll find out what’s in in before I list it, thanks.
           
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