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How much ratio does the torque converter add?

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    #1

    How much ratio does the torque converter add?

    Okay, I've been doing some math, here, and I'm trying to figure out what the actual first gear ratio is in an AOD when you add in the reduction from the torque converter. I was talking with my dad about it, and he figured that it'd be around 1.9:1. That means that the effective first gear ratio would be 1.9*2.4=4.56. With 3.55 rear gears, that would give a total reduction of 16.188:1 in first gear.

    Now, part two: I'm very seriously considering going to a T5 this summer (with the job I've got, I can afford it, so why not?). The one I'm looking at (FRPP M-7003-R58W) has a 3.27 first gear. 3.27*3.55=11.6085. That's a LOT less reduction than the AOD gives (assuming my torque converter reduction figure is somewhere near right). Does that mean that I'll actually lose off-the-line acceleration with the 5 speed? I'll be doing some engine upgrades as well, but for now I'd prefer to leave those out of the equation for sake of clarity.

    If anyone can shed some light on this, I'd very much appreciate it.

    Thanks,

    Nathan

    2001 Ford Crown Victoria P71 - "The Fire Engine"
    1985 Lincoln Town Car Signature Series
    But God demonstrates his own love for us in this: While we were still sinners, Christ died for us. Romans 5:8
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    #2
    No clue man....

    Well, with the 5 speed, 5th is usually more of an OD than OD in an AOD/4r70W, so more rear gear can be used to compensate. Also remember that the clutch is used to the same thing as a stall converter.
    Builder/Owner of Badass Panther Wagons

    Busy maintaining a fleet of Fords

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      #3
      A higher RPM converter dosent change your gear ratio. Basicly it is used to raise the RPM at which the fluid in the converter locks up. It is to allow an engine with poor low end torq to reach a higher rpm before lock up because the power band has beeen moved to a higher range. To high or to low of a range can hurt performance.
      Scars are tatoos of the fearless

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        #4
        Maybe he's thinking torque multiplication?
        Builder/Owner of Badass Panther Wagons

        Busy maintaining a fleet of Fords

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          #5
          Originally posted by mrltd View Post
          Maybe he's thinking torque multiplication?
          That's what I'm thinking too, cause them converters are supposed to do that and it kinda works like a lower gear maybe

          Comment

            #6
            it slips but i dont think it makes it like a lower gear..

            Comment

              #7
              Well, if the torque converter is slipping, wouldn't that by definition mean that the gear ratio is being lowered? For it to slip, that would require the number of turns at the output to be lower than the number of turns at the input. I'm just trying to get a real picture of how much total reduction I have, and whether I'll lose reduction with a manual transmission.

              2001 Ford Crown Victoria P71 - "The Fire Engine"
              1985 Lincoln Town Car Signature Series
              But God demonstrates his own love for us in this: While we were still sinners, Christ died for us. Romans 5:8

              Comment

                #8
                You get torque multiplication yes, but not mechanical multiplication like a gear. The converter doesn't factor into the amount of gearing you have, it does however factor into how much effective torque you can make. You're probably doing about 2:1 torque multiplication, but that still doesn't affect the actual gearing. Its effectively like riding the clutch on a manual. Yes the motor spins up more so it can make more power, but its not doing anything for the ratio of engine rpm to rear wheel rpm.
                86 Lincoln Town Car (Galactica).
                5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                91 Lincoln Mark VII LSC grandpa spec white and cranberry

                1984 Lincoln Continental TurboDiesel - rolls coal

                Originally posted by phayzer5
                I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                Comment

                  #9
                  Hmmm...interesting. In that case I guess I have nothing to worry about. But all my nice math was for naught!!!

                  2001 Ford Crown Victoria P71 - "The Fire Engine"
                  1985 Lincoln Town Car Signature Series
                  But God demonstrates his own love for us in this: While we were still sinners, Christ died for us. Romans 5:8

                  Comment

                    #10
                    Yes, Torque multiplication is something that can be manipulated with torque convertors. This is why certain completely-stock cars with automatics are quicker than 4-speed/5-speed cars, as the convertors are multiplying the amount of torque coming off of the flywheel, usually overcoming the parasitic frictional losses one sees in an automatic transmission (approaching 65-70 HP through a C6 tranny, AOD's are around a 35-40 HP loss, and C4's lose around 30-35).
                    Aftermarket convertors can be built with as much as a 2.5-2.8 to 1 torque multiplication ranges...most stockers are straining to reach 1.75-2 to 1.... but the best convertors are fairly spendy.

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