No clue what the proper operating temp should be for your rig. However, an auxiliary trans cooler is the common method to reduce trans temps.

 

not that accurate, B&M has a cheap trans cooler i used and now get better shifts and temps. if you really want to know you can put in a thermostat for fairly cheap and put a gauge in the cab. there are some write ups. pretty sure service manual says 150-200 degrees is normal operating temp and 240 is overheating on the 42RLE; if i remember right. mine runs much better now that i added that cooler. these transmissions run hot in the TJs.

 

Can we assume you have an automatic? With a full synthetic as the mandatory ATF+4 is, that temperature isn't a huge problem as can be with an older non-synthetic ATF. But if you regularly do things that are known to cause higher ATF temperatures like that, it would be wise to install a transmission cooler.

I have installed both a passive (no fan) cooler and one with a thermostatically operated electric fan and can testify the one with a fan works better in more difficult situations like slow-speed offroading, rock crawling, etc. Here's my writeup on my last installation... http://www.wranglerforum.com/f210/k...atic-transmission-alive-review-installation-of-derale-tranny-cooler-110676.html

This chart is more what would be expected with a non-synthetic ATF which is damaged by heat more than a full-synthetic like our required ATF+4 is.

 

Another automatic transmission cooling option is the Flexalite 4116TJ direct fit auxiliary cooler, $104.77 on Amazon Prime as of 4/25/18.

https://www.amazon.com/Flex-lite-4116TJ-Direct-fit-Transmission/dp/B018B6XDVC

It is a simple but effective auxiliary ATF cooler with no moving parts and more than enough capacity for 95% of us, even in 4-lo at low speed.

A solution that may desirable for one situation may not be the optimum solution for everyone or every situation. For example, what might be necessary for desert rockcrawling or trailer towing in the mountains might actually be a disadvantage in other environments.

Some potential advantages of the Flexalite cooler over the fan-based Derate cooler are lower cost, less complexity, no moving parts, and nothing between the frame rails to clog with snow or mud. Sometimes simpler is better.

The bottom line is that one should always carefully analyze one's particular needs and desires and not blindly follow anyone's recommendations for equipment modifications. Even mine.

 

I have that cooler on my '02. It's been there almost 2 years now. My little ol' 32rh definitely likes it. When I installed it, I had to pull the radiator and the ac condenser out to get it in. All in all I've been happy with it.