Question on fitting modern trans in 71 Demon

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a34

a34

The Etowah Flash
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Hey guys,

My son's 71 Demon has a 98 360 in it with a 904 attached. The 904 has been giving us some trouble. Depending on what the problem is and cost to repair, I'm thinking of putting in a modern 4 speed automatic. 518 maybe?

I'm wondering what parts are needed to make it work and if the floors have to be modified? Is a 518 the best way to go? What is the approximate cost? Can I do it with junkyard scrounged parts?

thanks !
 
The 518 is not the best way to go. The best way to go in today's Mopar world is the GM 200 4r transmission where there is no cutting of the floor and using a wilcap adaptor for the conversion seems to be what others are doing. The ratios are 2.74, 1.57, 1.00, 0.67 so using even a 3:23 rear will get you out of the chute a little faster than the 518 and the 200 4r is stronger.
 
Got to take into account that you can't just slap 200R4 in and expect everything to be fine.
It'll need a little work to be capable of lasting.
 
the a518 will bolt right up to the 360. the hot rod article is for a big block. then there are two on that has a lock up convertor and one that does not. these trans can be found in dakota and ram pick ups, not sure what year. with the lockup convertor you need to oil pressures switches a vacuum switch . look here they have info on this.
img3.jpg

there is more but i can't find it right now
 
There are photos of the transmission installed on the 42rh/a500 on the above posts.

I have installed the a500 in my 70 dart with out cutting the floor.You will have to cut the cross member on the upper side even if you do a 2004r.

I have seen both done and i think the a500/a518 would be cheaper and easier than the 2004r.
 
Hotlines, the 200R4 is stronger than what? Not a 518. The 518 is a 727 derrivative. The 200R4 is stronger than that 700 slushbox. Is that what you meant?
 
Well anyway you slice it, "it's been done"

Put a 200 in without chopping the floor

Otherwise be ready to rebuild the floor and crossmember.

Not in my car, you won't
 
the 518 fits in the dart with out cutting the floor the chevy will cost more just because you have to get adaptor. yes you have to change the trans mount but, i think you will have to do that with the GM200. and the drive shaft will have to be altered. i think you can go to a you pull junk yard pull the 518 trans . the rest should be under 300.00, pressure switches and drive shaft.
 
Thanks guys, great info as always. Lots of stuff to review and decide on here. My Saturday is full !
 
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