G3 rpm/gear ratio

New Hemi Engine Swaps

  1. 1973Barracuda

    1973Barracuda Well-Known Member

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    those that have done the swap, what ratio are you running? I have read different things as far as the rpm the g3 will be happy cruising at.

    I am ready to pull the trigger on a rear end, but want to buy once(hopefully).

    I thought I wanted a 3.55 or 3.23 to keep highway rpms down, but read it may be unhappy there.

    Thoughts?

    6.1
    46rh
    27 inch tire
     
  2. RealWing

    RealWing FABO Gold Member FABO Gold Member

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    What tranny OD ratio are you running?

    My 6.1 SRT8HEMI manual tranny has a 0.70 OD with 3.91 gears. In hindsight, a 3.55 gear would have been better for me - but depends on what you want to use the car for. You can calculate RPM with different setups using this: HyperMart

    Jim
     
  3. 1973Barracuda

    1973Barracuda Well-Known Member

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    .69 overdrive.

    I have figured the rpm thing, what I don’t know is where the engine is happiest.

    1800 at cruise on the highway sounds great until you find out it is a dog there.
     
  4. RealWing

    RealWing FABO Gold Member FABO Gold Member

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    The 6.1 is no dead dog!!!! The torque curve is very flat - especially at lower rpm.. eg
    300 ft-lbs @1200 rpm
    325 ft-lbs @1600 rpm
    340 ft-lbs @2000 rpm
    350 ft-lbs @2400 rpm
     
    • Agree Agree x 1
    • 1973Barracuda

      1973Barracuda Well-Known Member

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      Yeah, dog was probably a poor choice of words.
       
    • RealWing

      RealWing FABO Gold Member FABO Gold Member

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      Maybe, but I knew what you meant!! It was a legitimate question for sure.
      Jim
       
    • Chuckbizkits

      Chuckbizkits Well-Known Member

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      I'm running 3.89 with NAG1.
       
    • 1973Barracuda

      1973Barracuda Well-Known Member

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      Overall ratio and tire size please.

      How is the performance?
       
    • GoodysGotaCuda

      GoodysGotaCuda Mr. Goody

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      I have a 0.63 6th, 3.91 and 28.4” rear tires. I have no problems with highway crusing torque. If I started from scratch, 3.7x in the axle would be a hair better for me.
       
    • 1973Barracuda

      1973Barracuda Well-Known Member

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      Goody, you must cruise at really low rpms.

      With 3.55 I think I was looking at 1800 at 80mph I think.
       
    • GoodysGotaCuda

      GoodysGotaCuda Mr. Goody

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      at 65mph I am about at 1,900rpm, 2,300rpm at 80...

      If you had 3.55s, 0.69 OD and turned 1,800rpm at 80mph, you would have to have a 36" tall tire...the correct calculation is 2,368rpm using the 27" tall tire you reference earlier.
       
      Last edited: Feb 28, 2018
    • 1973Barracuda

      1973Barracuda Well-Known Member

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      Ran the numbers again. You are correct.
       
    • 1973Barracuda

      1973Barracuda Well-Known Member

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      2439 with .69, 3.55, 27s, at 80 mph
       
    • Buschi340

      Buschi340 Well-Known Member

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      4.10 is still good for Relaxing 240 km/h :)
       
    • 1973Barracuda

      1973Barracuda Well-Known Member

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      Buschi, what gear, Transmission, and tire size?

      Thanks
       
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