Gah, long post detailing my reasoning behind and concerns with each approach. Trying to do a couple of things at once, finally hit post, and
has logged me out.
I don't wheel, but I do have to drive through brush and unkept lanes, drifted snow in the winter, etc. I don't think the wiring from a sender would last even a year if mounted in the bottom of the pan.
Diesel, I don't really know. This is the first AT I've ever fooled with, having had manual gearboxes almost exclusively since I started driving. I think the fluid at the test ports has only been through the pump, not through the transmission itself, so I wouldn't be reading the "hot" temps. No idea if this is actually the case; I'm pretty clueless here, obviously.
There are different opinions on where to put the sender, how to mount it, which temp readings matter more, etc, and I'm still trying to figure this all out. I've never cared about fluid temps or what was going on, but I'm starting to use the Jeep to do more towing/hauling, and the transmission was pretty neglected for a long time. I've started playing catchup with maintenance, along with adding a cooler, replacing lines, putting a gauge on it, etc, which leads me to this.