A-904 Compatibility and changes?

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C2ndLTpigeon

C2ndLTpigeon

Mopar or no Car!
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Wanted to see if someone knows the difference in years of the 904?
For example rebuild kits will list 1960-1971 and 1971-1992.
Other than the obvious linkage setup on the outside of the transmissions what changed internally?

I have a 1971 /6 904 and 72 /6 904, yet the kit cuts of at 71 and the other starts at 72. Are the cases the same and just the internals?

Still learning automatic transmissions.

Thanks
 
The only thing I can think of that changed in the '71-'72 era was the introduction of the part-throttle kickdown valve body.
Many other changes earlier and later than that, though- the major ones are the input shaft size/spline pre-'68, pushbutton case (cable shift) and VB until '65, speedo drives changed in '67, ball and trunion (flange) output shaft until '65, Cooling line ports were increased to 3/8" sometime in the '80s (probably when they added the lockup convertor), lots of governor changes over the years, and probably lots more that I'm not aware of...
I have no idea why they grouped the years that way.
 
Thanks for the info, I was curious about them since at a glance it seems most things are interchangeable such as drums, shells, planets, case, oil pump.
 
C2ndLTpigeon said:
Wanted to see if someone knows the difference in years of the 904?
For example rebuild kits will list 1960-1971 and 1971-1992.
Other than the obvious linkage setup on the outside of the transmissions what changed internally?

I have a 1971 /6 904 and 72 /6 904, yet the kit cuts of at 71 and the other starts at 72. Are the cases the same and just the internals?

Still learning automatic transmissions.

Thanks
Click to expand...


In 72-73 the kick down servo diameter increased. In 78 the sealing ring diameter changed on the input shaft. Can’t remember the year, but the roller bearing on the output shaft changed dimensions. The wide direct drum used a front pump with a beveled back. Just a few I remember off the top.
 
The case was different between 70 and 71 right in front of the rear servo. The VB was different on the mating face to the case to match.
 
If it’s like a 727 the front drum will have a wider bushing in 72 up. The front drum will have a wider lip seal in the 71 back. I haven’t done a 904 in a lot of years so I could be wrong about these 2 things. Kim
 
Some pump/forward hubs had two rings some three; of the non-lockup variety. Like the 727. Some drums hold more clutches than others.
 
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