You can successfully flush your existing trans cooler with a can or two of transmission flush - here's the process:

 

Yea I'm just going to buy a new cooler. Truck has 200k on it might as well just put a new one on that's better than stock. But thanks atomic

 

you are correct that is the way it is usually done.
The reason I did it that way is when i first put the aux cooler on
I was running it by itself and in this weather it would not get warm enough to engage OD and converter clutch, from the FSM:

TRANSMISSION FLUID TEMPERATURE
THERMISTOR
Transmission fluid temperature readings are supplied
to the transmission control module by the thermistor
(Fig. 6). The temperature readings are used to
control engagement of the fourth gear overdrive
clutch, the converter clutch, and governor pressure.
Normal resistance value for the thermistor at room
temperature is approximately 1000 ohms.
The PCM prevents engagement of the converter
clutch and overdrive clutch, when fluid temperature
is below approximately 10°C (50°F).
If fluid temperature exceeds 126°C (260°F), the
PCM causes a 4-3 downshift and engage the converter
clutch. Engagement is according to the third
gear converter clutch engagement schedule.
The overdrive OFF lamp in the instrument panel
illuminates when the shift back to third occurs. The
transmission will not allow fourth gear operation
until fluid temperature decreases to approximately
110°C (230°F).
The thermistor is part of the pressure sensor and
is immersed in transmission fluid at all times.

So I ran it back thru the radiator cooler to maintain proper temp.
The factory cooler is located between the radiator
and air conditioning condenser, mine is in front of everything.
I dont know if anyone with factory coolers have the same issue in this weather.
So that is why I ran mine the way i did.

Dave
__________________
96 Ram 2wd 5.2L Auto
86 Dodge Ram /6 with HEI conversion.

 

When excessive cooling is a wintertime problem, I like to use a fluid control thermostat to (automatically) bypass the external cooler. Works a treat, and leaves the system prepared for summertime heat, too.

 

Are you planning on using the cooler in the radiator? Or are you just going to use an external cooler?

I would suggest one of these two. The B & M super cooler is what I run on my Jeep but mine doesn't have the fan on it. I am going to swap it out for one with a fan also because I am not going to use the radiator. I also use one for my power steering as a cooler too.

B & M Super Cooler w/Fan


Flex Lite Cooler W/Fan

 

Yea I'm going to try hooking it up to my radiator for some odd reason 2 years ago when I had a shop rebuild the transmission they ran the lines to just the external and by passed the radiator. Not sure why. It was a ****ty ship they are out of business now.



Also where is the best place to mount a temp gague sensor in line or in the pan?

 

In the output line TO the coolers, as close to the trans as you can get.

 

If you use the B&M guage kit, be careful of the brass T fitting for the sending unit.

The nut cracked on mine, and the compression ring never got tight enough to seal.

Happened on 2 different installs (Both Jeeps, one with the 32rh and one with the 42rle)

On one I put the tee onto copper tube, and used rubber hose and dual clamps on each side. (you must ground the copper tube for the guage to work)

The other I never did fix (just bypassed the T), as I was already over the Rockies when it started leaking, and never had any temp problems.