Exactly. The engineers haven't always come up with the best solution that fits our needs. For me personally, I have bypassed the radiator entirely for my trans into a plate-and-fin style cooler. I live in PA, and the winters get cold--I first am going to experiment to see if this will really be an issue with my scenario or not. I just purchased a trans temp gauge (finally) last night so that I can actually monitor what's going on. If it becomes a problem, I'm going to rig the cooler before the rad. The less heat going into the rad, the better. I also plan to place another sender unit on the return line to see the cooler's effectiveness.

Steve, do you have a wiring diagram for how you have yours set up? (you do have a switch to toggle between them, right?)

Looking forward to the results. Hope u don't go from 175 to 210 like the OP did.

I also ran an auxiliary cooler only, for a full year. Temps stayed below 140F on highway (hot line) IR temp gun read the pan at 150F.
Around town it would run 160.
On beach 180-190F in 4-High, switching to 4-Low temp quickly drops to 150F.

Using two separate gauges and senders. Mechanical sender in port on AW4 and electric sender in hot line.
The hot line is exiting the torque converter which will add more heat to the fluid depending if it's locked/unlocked, this reading is fluid temp but not overall transmission temp.

Here is a link to location of sender port, 1998 and earlier AW4. Courtesy of forum member CCKen.
Post #48 https://www.cherokeeforum.com/f2/gre...4/#post2851314

Wonder why the hot line fluid temp (140) would be lower than the cool pan fluid temp (150)? Seems like it would be the other way around, no?

Actually 1998 is when they changed it and blocked it off. I know my AW4 doesn't have that port in my '98. That's okay though, I'll just pipe them in with the cooler lines.

From what I could figure and explore with a temperature gun, the electric sender in hot line is 2-3 degrees lower than what the infra-red gun states. And the sender is placed at the end of metal line, which is about four feet long and exposed to airflow, especially in the front. That metal line seems to dissipate heat at highway speeds, accounting for the difference.
This is another reason I prefer to know the overall temp of transmission, rather than the fluid.

FYI. After jeep has been driven, the difference between inlet/outlet of auxiliary cooler is 18-20 degrees, at idle, cooler mounted in front of HD fan clutch. B&M plate+fin 11" x 7" x 3/4" (the 1.5" thick unit would not fit).

If you decide to install a sender in the pan, it must go in a specific spot to clear internal parts.
There are fittings that will replace the drainplug with a sender.

That's an idea, problem being the drain plug points straight down. I don't play around on the beach like you do though so I might be okay with just fluid line temps

.....and how is the overall temp determined?

Temperature port on AW4. Toyota used it but Chrysler never did.

Infrared guns are not accurate on shiny silver objects like aluminum cooler lines. Cover target area of line with flat black paint.

Good tip, thank you.

.....so overall temp and fluid temp r one in the same?

No, fluid exiting the torque converter and fluid in the pan are often 2 different numbers.
What's next..

Just trying to figure out where u r coming from. Overall temp, fluid temp, now pan temp.....who knows what's next.