i have the slant six and i remplace my rear axle 7 1/4 to 8 1/4 but what i can use on this combo i have the 3 manual speed but what if i remplace it whit the 3 speed auto? thats better ?

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That consume your mind, that's controlling your life

It really depends on what you want to do with your car....

The manual tranny:

Has no torque convertor slippage, no bands to adjust, needs no tranny cooler, no filter or fluid to change...linkage and bushings can get loose and sloppy, can burn up the clutch after a whole bunch of hard launches...
Can also be a pain if 1st gear is not synchronized...may need overhaul if has very high miles and abused.

You can push start the car on an almost dead battery after getting it rolling and popping the clutch...

Auto tranny:

Is relable if maintained, no clutching or shifting required, unless desired at the shifter. Much more consistent at the drag strip than the manual tranny. May require different torque convertor depending on gearing and engine build...Typically has 5% loss of power due to slippage, except the lockup versions in 3rd gear at highway speeds. Requires kickdown linkage to be properly installed so it will downshift to pass/accelerate positively. Requires tranny cooler at tranny, lines to radiator from tranny,

Late A904 has lockup capability, some versions have partial kickdown capability, supposedly versions up to mid-60's can be push started if you get it up to 35 mph and drop it into low...


But my list isn't 100% definitive...

thanks for reply , i need to say the engine 225 will be "upgrade" i have the 3 manual trany whit floor linkage but i like the know if i have better performance on 3 speed torqflite? cause i will remove this gearbox from another duster in junkyard, the duster have a complete shift console and engine 225 inside like my duster

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That consume your mind, that's controlling your life

The distinguishing factor is whether it has a rear oil pump. For A-bodies, the 65-older ones did. The 66-newer ones did not. (I'm sure we can thank the bean counters at chrysler for telling the engineers to remove anything that could even remotely be considered non-essential.) Not only did the rear pump allow push-starting, but it allows the vehicle to be flat-towed without any risk of transmission damage, because fluid is pumped when the driveshaft turns.

My 65 Valiant 170 could be push-started. I'm pretty sure that dropping it into "D" was sufficient. I don't believe I had to be rolling anywhere near 35mph to accomplish it... but that car was a a few decades ago and it seems my brain did not consider the specifics to be worthy of saving. In the Early A-bodies, I've enjoyed nothing but standard shift transmissions since then.

- Erik

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Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

you say a 60 trany go better?

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That consume your mind, that's controlling your life

Hola amigo!
My '78 Volare has a 225 slant six, and a 904 automatic transmission.
Years ago, I removed the 7 & 1/4 differential and installed an 8 & 1/4 differential. I had to have my driveshaft shortened 2 inches.

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"Ja, Ich fahre ein altes auto."
'78 Volare 225
'67 Charger 318