In the bottom, base ling 4 door, 225 Valiant, what transmission did they have(automatic) 2 speed or 3? if so what kind? And what kind of rear and gears do they have in them?

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-1970 Pontiac Firebird Formula 400
www.cardomain.com/id/ramair70formula

If its an automatic, it is a TorqueFlite 904. The rear will be a 7 1/4", either a 2.94 to 1 or 3.21 to 1 ratio. Nice Formula BTW.

Is that a good transmission?

Also, would it be a good idea to drop in 4.10 or 3.73 gearing?

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-1970 Pontiac Firebird Formula 400
www.cardomain.com/id/ramair70formula

Yes the Torqueflite 904 is a very good tranny. It will last a long time behind a slant. It has very low parasitic power loss also, pretty close to a powerglide. If you want more zoom, install some V-8 904 parts which lowers the first gear down some more.

I would not recommend swapping in any gears lower than 3.55 in a street car. My Duster used to have a 3.91 rear under it. Although I enjoyed zoomimg around town and bouncing imports in it, the gas mileage was terrible and with the engine doing @3500 RPM at 60 MPH, it sounded like you were riding in an airplane. Lower gears also means decreased engine and accesory life. I recommend either 2.92 or 3.25 gears out back plus a Super six setup and a cam out of a 70's slant. This will give you pretty good acceleration and decent gas mileage. Remember, it is a six cylinder, so don't expect too much out of it.

Nice Firebird, by the way . How many imports have you whipped with it?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Sorry Jeb.
The low ratio first gear set for the 904, was in the late model trans (don't remember what year they started). They can be swapped into the 66 and later trans, if you also use the late model torque converter (67 up).
The low ratio gear set cannot be swapped into the 65 and older trans, been there, tried that, won't work.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225