Technical 904 transmission

Hi all, I am trying to install a 904 transmission behind a 318 small block for my 1950 Plymouth. Are all 904 Transmissions the same, I have a 1989 904 and a 1969 904, I wanted to use the 1989 transmission so I change the front seal and filter but I cannot seem to get the torque converter sank all the way down in the 89 transmission. The torque converter will however go all the way on the 69 transmission. I'm not sure what is going on whether I have the wrong seal or the torque converters are different from 69 to 89 or the transmission is different from 69 to 89. Any help would be appreciated thanks.

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I think if you look at the imput shafts of the two transmissions you'll find they are different.

 

The '89 transmission will most likely use a lock up converter, the '69 uses a regular non lock up converter, so you can't mix and match them.

 

lock up started around 1977, not all of them had it at first, but by 89 they probably did.

also beware the converters for different engines are balanced differently, for example the 360 requires a good sized weight on it, while the 318 (at least the older ones I"ve worked on) don't.

 

It's the input splines....18 verses 21 I think.....ask me how I know....the transmission shop screwed up my converter by not paying attention when I took it in for a rebuild

 

And what Jim said on 360 motors......

 

The later one is most likely a 998 , when they started using high rear end ratios they put a lower low gear in and a lockup convertor.If that it the case will have an extra feed for the lock-up .

 

the lockup has a little smooth area at the end of the input shaft splines, about half an inch long. Pretty easy to spot.

 

So I think everyone is correct it is a lock up trans, I have been trying to decode the numbers, only thing I have figured out it is somewhere between 1981-85. Correct???

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yeah, but one of those stamped number tells you the build date, you could probably find how to decode it and get it more specific, if it matters.

I forgot which one it is, and I'm too lazy to look it up. The part number is 1981-85, as you said.

 

It is 8475 bit not real sure how to decode it

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according to the fancy internet date decoding page, it's

Day 8475 is Wednesday, October 10, 1984

 

you didn't stay lazy very long.....

 

From Car Tech's new book on Rebuilding 727 and 904 transmissions, it is a 1981-85 truck version. 4058398 318 A-999 Wide Ratio-LU

also in a 1982 -1985 car. 4058398 318 A-999 LU-

 

I found that fancy page!!! Thank you for the help

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the list I downloaded a while ago shows a lot of applications.

 

Thanks for all the help

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Great, our data matches! The good thing is it is a wide ratio lockup which will be good for some mileage and off the line performance.

 

ok, so I got a torque converter from my friend that gave me the trans, it is the proper converter, as I was carrying it to the car I shook it and heard something inside move, there is no fluid in it. is that normal??? I would hate to put it all together and find out it is bad and drop the tranny again??? again, thanks for your knowledge!!!

 

Yeah, that is normal.

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