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Gear ratios and stall converters

Discussion in 'Gearheads' started by swampratt, May 3, 2021.

  1. swampratt

    swampratt Sharpshooter

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    Some things to think about.
    For best launch you would think a 4.56 rear gear would come out of the hole better than a 3.73
    rear gear.
    Yes it does but if you have a low stall torque converter (2000 RPM) with the 4.56 rear gear you may not get out of the hole as fast as a 3.73 with a 4000 RPM converter.

    Speaking of a vehicle that gets traction, not one that spins the tires.

    When I dealt with lighter cars for the strip the Powerglide was choice.
    1.76 First gear in most of them and we would stick in a 5.14-5.46 gear but with a 32-33" tall tire.


    How about a 3.89 gear with a 2 speed Glide and a shorter tire.
    Would you run a 4000 stall to get a good launch.
    I would or maybe a bit more stall speed.

    The reason I bring this up is a little math 1.76 first gear in the Glide X 3.89 rear gear.
    You get a 6.84 first gear ratio.
    Lets look what happens with a 3 speed TH 350 with a 2.52 first gear.
    2.71-2.73 rear gear puts you right in the 6.84 first gear ratio.

    Yes a Highway gear and the TH 350 is darn near the same as the Glide with a 3.89 gear.

    You would not go drag racing with a 2.73 rear gear and launch very well.

    Or could you????????

    Lets say you used a 4,500 with that 2.75 rear gear and the TH 350..What happens now?

    When I was setting up my 57 for a drag race against my friends 550 Wheel HP mustang i pulled the 3.73 gears and stuck in some 4.56 gears.

    The launch on the street during testing still felt weak.
    I pulled the 2500 stall and stuck in a 4500 Stall Coan converter.

    Now it felt right I got a great launch with it.

    If you make enough TQ I think you could do well with a 2.75 and high stall with the TH350

    I may be testing that theory soon.

    Fun with numbers.
     
    O4L and MacFromOK like this.
  2. Snattlerake

    Snattlerake Sharpshooter

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    I hate math.
     
  3. Profreedomokie

    Profreedomokie Sharpshooter

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    I'm in the middle of installing a LSD in my Fiat 500 Sport now. With 30% more HP than stock and the handling of a slot car it is a blast to drive on twisted roads.
     
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  4. swampratt

    swampratt Sharpshooter

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    My son had a MX5 that was the $H!t around corners and pretty quick on the straights.
    He drifted it for a bit and got bored with that.
    For a Miata it looked pretty darn good.
    [​IMG]


    [​IMG]

    [​IMG]

    [​IMG]


    Hope these all show up.
    Hoosiers and different wheels for some stupid grip in the twisties.
    [​IMG]

    A stripe he painted on with Plasti Dip one on the trunk also.

    [​IMG]

    upload_2021-5-4_10-54-5.png
     
    Biggsly likes this.
  5. wawazat

    wawazat Sharpshooter

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    I spend a LOT of time on a gear ratio calculator before selecting a few final drives to start digging into. There is a lot that goes into it if you want to be competitive at the track. Cam selection, rev range, OD of your tire, OD growth if running bias ply tires, transmission ratios, what kind of power adder if any, and stall if running a two pedal car.

    I definitely prefer the removal of the torque converter from the equation, but I build stuff that is fun for me to drive not so much strip focused. The next car may be a little more drag focused but only because I really want to run a Lenco for some reason haha.
     
    swampratt likes this.
  6. MacFromOK

    MacFromOK Sharpshooter

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    Lol, I hear ya. :D

    I can get by with math (have to when computer programmin'), but we're not exactly friends...
    :drunk2:
     

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