Home Forums Technical Questions The Official KCW Gear Ratio Calculator

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  • Willy
    Moderator
    Post count: 690

    So John and I put this calculator together a while ago when I was figuring out what R/P  and other gear ratios I wanted to have in my Westy, figured I’d share it with all of you for a resource

     

    You can check it out here: KCW Transmission Calculator

     

    There are 4 scenarios right now; the Pamper, Franz’s 66, my Westy, and an open slot for you to play with.

    To start, put it your ideal cruising speed (I usually do 65)

    Then you put in your ring and pinion ratio (Usually 3.44, 3.88, or 4.12)

    Next put in your 4th gear ratio and then your tire diameter in inches (if you don’t know you can look here)

    Reduction boxes can get a little more complicated because they’ve often be re-geared later or whatever, but if they haven’t been messed with a big nut is 1.26, small nut is 1.4, and straight axle is 1. 

    Once you have all that in you can see what RPM you’d be turning at whatever cruising speed you set and then play around and see how it changes things. Keep in mind that it doesn’t take engine size into account, so you could easily put together a setup using this that you couldn’t actually turn due to a lack of power….

    IMG_6471

    Franz
    Keymaster
    Post count: 2369

    Hell yeah Will.

    How do you like your combo for driving around California?

    John Jones
    Keymaster
    Post count: 4697

    this is super cool!!!!!    For some reason I thought you, WILL, had the .082 4th also… guess not,,, That would really be high!!

     

    I LOVE my 3.44 r/P…. best combo I have ever had…

    Franz
    Keymaster
    Post count: 2369

    My cruising speed is 70-75mph I can keep up with interstate traffic.

    Utah’s 80mph speed limit has me wanting a 3.88 though.

    Franz
    Keymaster
    Post count: 2369

    I don’t like the “freeway flyer” (stock bus)  .82 4th. The rpm changes between 3rd and 4th gear shift is too much for our hot rod engines.

    The bigger cam in a hot rod engine has less low-end torque and kills the hill climbing on the interstate when you have to down shift.

    Another cool side effect of putting the 3.88 or 3.44 in a gear reduction bus is that it loads first gear more. This is good for accelerating from a stop light…..the rear suspension doesn’t lift and “clang” on the spring plate stops as bad.

     

     

    Wren
    Participant
    Post count: 124

    Thats pretty cool… What would my 4th gear be at with that 4.37?  I’m still not sure about that gear box I have.. I think a 4.12 would be cooler. I like the low gears so far but it feels like I need a 5th gear.

    Franz
    Keymaster
    Post count: 2369

    Stock bus is .82 4th.

    You should go for a 3.88 x .89 4th with reduction boxes and 1914cc.

    There are also special option alpine reduction gear boxes that have a different ratio. I hope you don’t have those.

    Willy
    Moderator
    Post count: 690

    Hell yeah Will. How do you like your combo for driving around California?

    I really like the gearing out here. I don’t have any problems pulling away from stoplights quickly or hill starts or anything.

    The other great part is that I don’t feel like an obstacle on the highway and I have ample gearing to speed up and pass someone if I need to!

    Willy
    Moderator
    Post count: 690

    Thinking about it now, the only times I’ve really had trouble climbing is on back-roads when I don’t hit a hill revved up, which I think is due more to my big ports and less because of the gears.

    Jb
    Participant
    Post count: 431

    Sweet! I ran what I think is in this IRS box from Parker and @65 I’ll be a pussy over 3k

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