Are there different gear ratios that can be fitted to a 904 Automatic transmission?

If so, how can one calculate what the transmission has for a gear ratio.

Presently I have a 3.55:1 8 3/4 rear end. My goal is to create a taller final ratio by transmission recalibration to improve gas milage.

I know, I can hear you; "just change the rear end". My 904 currently is fitted with a reverse valve body, and needs to be returned to normal operation. In this case a change of transmission gear ratio would be easer if possible.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

There are only two ratio sets available. Through 1980, the ratios were:

2.45, 1.45, 1.00

Starting in 1981, the ratios were:

2.74, 1.54, 1.00

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

As you can see by the info Dan posted there is no change possible to the final (high gear) ratio of the A904 as it's direct drive. You're stuck with a rear axle gear change, adding an overdrive or changing to an overdrive transmission. The only overdrive transmission that directly bolts up is the A833OD manual 4-speed. Adding a Gear Vendors OD to the A904 is also possible, but expensive.

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Joshua

Go with the Gear Vendors overdrive. It's spendy buy you'll really like it. Your final drive would be like having a 2.77 gear with it.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Maybe I'll liberate two of the 17" wheels shod with P235/65 rubber on the wife's Nitro... That would change the ratio a bit.

What was I thinking... Any damn fool knows that these old three speed transmissions have a 1.00 final drive. Gezz... I must have spent too much time clay baring & waxing the fleet today. Sorry to waste everyone's time.

Smicomatose Maineac

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC