Differential Pick

General Discussion

  1. Edward Cafiero

    Edward Cafiero Member

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    I will like to say first, thank you for all the help you guys have provided me.

    I purchase a Edelbrock 2086 TOP END KIT which will produce 421 HP with 417 Torque. Additionally, I purchased from Silver Sport Transmission an A41 Automatic 4 Speed transmission. I would like to know which diff ratio would be best for state to state driving and cruising. 3.23, 3.55 or 3.91.

    Once again, Thank you.
    Ed
     
  2. Don Frelier

    Don Frelier FBBO Gold Member FBBO Gold Member

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    Is 4th gear overdrive? and if so what is the reduction?
     
  3. 5.7 hemi

    5.7 hemi FBBO Gold Member FBBO Gold Member

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    How tall are the rear tires?
     
  4. diesel_lv

    diesel_lv FBBO Gold Member FBBO Gold Member

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    4sp n 400+ tq, state to state driving and cruising, go 3.23. Plenty of torque to spin them if you want. If you're racing, that's another matter.
     
    • Agree Agree x 1
    • Runcharger

      Runcharger Well-Known Member

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      I like a combined final drive in the 2.75 range for a highway cruiser with appropriate built engine (camshaft etc.). It's all about the complete package.
       
    • Edward Cafiero

      Edward Cafiero Member

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      Going with original 15" tires.
       
    • Edward Cafiero

      Edward Cafiero Member

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      I will have to ask about those items you mentioned. However, the A41 Ratio are 3.06, 1.63, 1.00, 0.70.
       
    • Edward Cafiero

      Edward Cafiero Member

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    • Don Frelier

      Don Frelier FBBO Gold Member FBBO Gold Member

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      0.70 would be overdrive and a fair amount at that.
      Maybe something like a 3.91 gear would work well
       
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      • WileERobby

        WileERobby Well-Known Member

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        Yeah, my thoughts as well. With that OD, the 3.23 are out.
         
      • 5.7 hemi

        5.7 hemi FBBO Gold Member FBBO Gold Member

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        Let be more specific, how tall are the rear tires? 28, 29, 27 inch?? That makes a difference.
         
      • diesel_lv

        diesel_lv FBBO Gold Member FBBO Gold Member

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        Use this rpm calculator. Determine what kind of highway speeds you'll be driving. Then determine what kind of rpms you want to be turning at those Highway speeds. All that's left is to figure rear tire diameter and diff ratio. W a bone stock 2bbl 383 and 2.92 gears, my car would broil the back tire without power braking.
        https://www.reillymotorsports.com/speed-tire-rpm-calculator.html
         
      • Edward Cafiero

        Edward Cafiero Member

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        Thank you very much.
         
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