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Speedster RPMs

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  • Speedster RPMs

    Hi, My 55 Speedster is great with a standard shift overdrive setup that I think is rare. The problem is I live in a very hilly area so hardly ever use the OD. At 60 MPH it's turning over at exactly 300RPMs out of OD. What RPM are Speedsters turning at 60 with an automatic and does anyone know what the Rear end ratio is for my car?

    I guess an additional question is will I be harming my 259 running at 3000RPM ?

    Thanks guys
    Life isn't about how to survive the storm, but how to dance in the rain !


  • #2
    Sounds like you have a 4.11 rear, AT would be a 3.31 and about 2500 RPM. 3000 RPM will cause no real harm, the 4.11. and even 4.56 were a late option for AT Avanti's and Avanti powered cars.


    63 GT R2
    63 Avanti R1
    63 Daytona convert
    63 Lark 2 door
    62 Lark 2 door
    60 Lark HT-60Hawk
    59 3E truck
    58 Starlight
    52 & 53 Starliner
    51 Commander

    JDP Maryland


    • #3
      You probably mean 3,000 RPM's. .

      If you have 205 75 15 tires or the equivalent height bias ply tire, 3,000 RPM's and 60 MPH means you have a 4.09 rear end.

      You can go here to calculate with other tire sizes if you need to...

      You could also look at the back of your differential cover. Under one of the bolts there should be a metal tag with two numbers on it. Divide the big number by the small number and that will give you your rear end ratio.

      My 54 was originally an automatic and came stock with a 3.54 rear end ratio. With that rear end, and the above tires, 60 MPH would be at 2,600 RPM's. With a 3.31 rear end ratio and the above tires, 60 MPH would be at 2,450 RPM's.

      Dick Steinkamp
      Bellingham, WA


      • #4
        quote:Originally posted by hotwheels63r2
        you should be able to get the car slowed enough to stop by keeping the RPM's up.

        Dick Steinkamp
        Bellingham, WA