63 904 trans dilemma

[1mean7Ddart]

My brother-in-law just acquired a 63 Dodge dart slant 6 904 push button transmission. The transmission struggles to switch gears. Would it be best to switch out to more later model 904 or rebuild the original. In my opinion I would find a cheap later model 904 and install a aftermarket shifter.

 

[abodyjoe]

is it push button? if so I'd do everything i could to use it.

 

[Workingdog1]

My brother-in-law just acquired a 63 Dodge dart slant 6 904 push button transmission. The transmission struggles to switch gears. Would it be best to switch out to more later model 904 or rebuild the original. In my opinion I would find a cheap later model 904 and install a aftermarket shifter.

I'm hopefully in the final stages of same dilemma and finding knowledgeable experienced folks to do the work is pert near the biggest challenge. Two cables for shift and park mechanisms plus availability of cables is another concern.

I'm gathering parts to go to a 4 speed and be done with it eventually.

 

[Professor Fate]

A later transmission will have a larger diameter nose on the torque convertor and won't fit the crank pocket (register) on a '67 or older engine.
And no, you can't mix torque convertors between early and late 904s- the input splines are different on the two transmissions.
Early 904s have a ball and trunion output shaft, later 904s use a slip yoke.
Early 904s have a different speedometer drive than later 904s.

By the time you
A.) disassemble the engine to have the crank pocket enlarged by a machine shop
or
B.) have a custom convertor made for the later 904 that has a small nose like the early trans and later model splines

and then buy a new floor shifter and have a new driveshaft made, you will have exceeded the cost of rebuilding the original transmission.

 

[MV8]

I would make sure the push button shift cable on the trans is adjusted so the valve in the trans is in the right position when the button is pushed. It may just need some maintenance (fresh fluid and a quart of Lucas oil, filter, lube cables, band adjust, etc).

 

[1mean7Ddart]

A later transmission will have a larger diameter nose on the torque convertor and won't fit the crank pocket (register) on a '67 or older engine.
And no, you can't mix torque convertors between early and late 904s- the input splines are different on the two transmissions.
Early 904s have a ball and trunion output shaft, later 904s use a slip yoke.
Early 904s have a different speedometer drive than later 904s.

By the time you
A.) disassemble the engine to have the crank pocket enlarged by a machine shop
or
B.) have a custom convertor made for the later 904 that has a small nose like the early trans and later model splines

and then buy a new floor shifter and have a new driveshaft made, you will have exceeded the cost of rebuilding the original transmission.

Oh wow. Thanks for all the info I just assumed that all 904s were interchangeable except for the push button type

 

[Workingdog1]

A later transmission will have a larger diameter nose on the torque convertor and won't fit the crank pocket (register) on a '67 or older engine.
And no, you can't mix torque convertors between early and late 904s- the input splines are different on the two transmissions.
Early 904s have a ball and trunion output shaft, later 904s use a slip yoke.
Early 904s have a different speedometer drive than later 904s.

By the time you
A.) disassemble the engine to have the crank pocket enlarged by a machine shop
or
B.) have a custom convertor made for the later 904 that has a small nose like the early trans and later model splines

and then buy a new floor shifter and have a new driveshaft made, you will have exceeded the cost of rebuilding the original transmission.

As a side note I needed a bushing or whatever you'd like to call it going from 318 to 340 that was a challenge to find for the crank pilot size.
Ugh !

 

[Professor Fate]

As a side note I needed a bushing or whatever you'd like to call it going from 318 to 340 that was a challenge to find for the crank pilot size.
Ugh !

That's for when installing the early trans on a late motor- opposite of what the OP is proposing to do.

 

[Workingdog1]

That's for when installing the early trans on a late motor- opposite of what the OP is proposing to do.

I understand but you know how search works and sometimes others find nuggets buried in the rabbit hole, try as you might it's inevitable imo.