I have been trying to get a realistic temperature measurement of the AW4 trans fluid. I was after the fluid temp at its highest point. Searching the threads here and on other lists, I found two general solutions. One group would fab a tee and insert the temp sensor into a splice in the trans cooler line leaving the transmission. The second approach removes the plug (My XJ is a '96) in the transmission case pressure test port and inserts the temp sensor at this location. The port is just above and about an inch forward of the trans cooler out line.

I have assumed that the fluid at this point is at the same temp as the fluid exiting to the trans cooler in the radiator. However, my temp measurements are strange - starting at 200F and ending up at 300F after about 30 minutes of stop and go driving.

My question for anyone with knowledge of the inner workings of the AW4: where does the fluid at the pressure test port come from and where does it go?

 

I am familiar with that port but not what is behind it. Chrysler never used it but Toyota did. The Yota guys might know

First step, I would use an infra-red temp gun to confirm that sender is accurate, and shoot various spots on the tranny also.

I have the sender in the hot line, exiting the torque converter, as you mentioned it should be similar/close to the what the test port reads.
For me, when hot line reads 180 driving in soft sand, tranny pan reads 155 with an IR temp gun. I deleted the stock heat exchanger in radiator.