I have a 96 Dakota 4X4 that I bought with the tranny sitting in the bed. 318, 46RE, NP231HD, 3.91 gears.
Just has the factory cooler within the radiator, I have an add on one here that is collecting dust (pretty big plate style one at that) hanging on a nail in the garage, it's time to put this dust collector to use, now that I have the freshened up trans bolted back into the truck.

I am not going to totally bypass the factory cooler, I have never had success with a tranny lasting if I didn't also plumb it in along with the factory one.

I THINK that I remember how to plumb these, I'm asking you guys to check my memory to see if I have this right.

From the tranny into the new aux cooler, out of the aux cooler, into the factory cooler at bottom of radiator, and back to tranny. Right or not?

Now for the real questions; mount this in front of the AC condenser or sandwiched between radiator and condenser?
and
would it matter if I put the fittings for the aux cooler both at the bottom, or would I be better to mount them horizontally? (with the inlet at the top of the new cooler)
or does that really mean much?

I think you'll be good going from new cooler then through rad cooler, then to trans. More important is to flush that rad cooler as good as you can before filling it up with the new atf.

already did flush the rad cooler.

I've never had an issue running a trans cooler without using the rad, (stick rad, with auto added through the extra cooler only) in the northwest corner of IL, for 12 years in a snow plow. Same trans, not rebuilt. I fail to understand why you want to reheat the trans fluid up to 200+ degrees before you send it back to a hard working trans.

But, if you feel you need the rad cooler, have at it. To be useful, the rad cooler would need to be the last cooler the trans fluid passes through before returning to the trans.

Mount the cooler in front of the AC condenser, and point the hoses whichever way is easiest to connect. Gene

my self I run it out of the trans into the rad cooler then into the aux cooler back to trans.

this way in the winter it will warm the fluid up to temp and keep it there. In the summer it cools down to engine temp then goes out in front of rad in fresh cool air to cool down more for the return into trans.

extra would be deep pan and reroute lines away from engine/header heat.

I run a oil cooler/ trans cooler/ PS cooler from a 88 fury police car on my 88-440 truck.

plumbed my own hard lines with some of the factory lines using factory coolers.

I have looked elsewhere for suggestion, as I used to put coolers in all my A/T equipped vehicles, (that's one reason I like driving stick.... less to go wrong) but it has been a while, had a few sticks and what autos I have had have come with coolers already there (couple of ex police Diplomats, fleet-equipped XJ Cherokees) so I haven't had to put one in for a few years.
Most say rad cooler 1st, then aux, then back to trans. incl factory sites for cooler manufacturers, though I remember running them the way I stated in an above post before?

Gene; We tried my brother's 80 Ramcharger w/a plow with just an external cooler; trans didn't last a season, went back to rad cooler and aux and no more issues, as soon as you get a wave of snow go over the plow and clog the fins that trans is done. even though it's cold, they need air flow to work. though I have seen some later 90s/ up-to-'01 Dodge trucks that have only got an external cooler from the factory, weird. I am also in Illinois (yuck) almost an hour south of Chicago (well, Comiskey park anyways, the only good reason to go into Chicago itself, ha ha) and work for the State, the trucks without rad coolers I have seen have mostly been full sized, 3.9 2wd trucks....

I'd recommend plumbing the add on cooler after the factory cooler.

That's the way the factory does it.

ok it's plumbed, rad cooler 1st, aux 2nd. Next will probably be a tranny temp gauge when I do the 1st pan drop..... which probbaly won't be as soon as i'd like, as long as the trans acts as it is supposed to... ATF+4 must have gold dust in it, too expensive to waste.....

I had to hit up wal-mart for their brand ATF4 because it was so much cheaper then anywhere else I looked at.

yup. have 2 walmarts within 10 mile radius of home, like when I did my wifes Durango trans, I had to buy out what stock they had between both stores.
They only put 6-9 quarts on the shelf at any one time, max, and when I ask, they claim to never have any cases in the stock room...
When I went to fill this one, the north walmart had a whole 3(!) quarts on the shelf, I was able to get the guy behind the counter at Oreillys to match the walmart price, just over $2/quart difference, $3/quart if I'd have opted for Valvoline. that's alot of money! Why does this fluid have to be so damn expensive?

Because it's synthetic.

When I swap the transmission in my other Dakota (92) think I'll head straight to O'Reilly and see if they will match Wal Mart price again, being as how O'Reilly has it in gallon jugs instead of quarts. My 96 took 11-1/2 quarts on a fresh rebuild with an empty fresh reman converter and the add on external cooler that I added.