Just put on my new deep DPP transmission pan. I drilled and tapped the pan and installed my sending unit in the pan. i have a autometer gauge. it starts at 100 and ends at 250 degrees. what is considered normal and what is considered hot as far as the pan oil temperature.

 

Anything over 220 and the fluid starts to break down very rapidly. The pan is really not the best place to put the probe at since it doesn't read the hottest part of the fluid.

 

Probe in pan is 100% better than no probe at all...just be aware you are reading averages.
Stock tranny, with probe in pan, may not get any reading in the winter...unless stuck in traffic. This is normal.
I would expect 130-160* on the hwy, after fluid warms up. Without synthetic ATF, I would put it in neutral and cool it down anytime it hit 200*; or just get into clear ram air. The more often you get over 200*...the more often it needs changing.

RJ