HemiDrivr, no, no leakage issues. I'm happy seeing the temp of the oil entering the pump (sump temp), as an "overall" temp for the box. What's coming out at the feed to the cooler is probably more indicative of the temp within the clutch packs, which is a more critical temp though, in all honesty.
HemiLonestar, the main reason I fitted a separate gauge and sender is that the thermistor within the solenoid pack that gives the temp signal to the Powertrain ECU is known to be somewhat "wide ranging" (inaccurate!). I have 4 solenoid packs here, the thermistors all indicate differently at the exact same temp. The difference from highest reading to lowest reading is over 20 degrees c, when all are at the exact same room temp!
2003/4 2500 Quad-Cab, Hemi-powered and running on LPG.
7.5 ton electric winch, hidden behind front bumper and powered by an intelligent split-charge system with twin 130Ah batteries.
On-board air, 2.5 gallon tank and a pair of British Rail Class 55 Deltic locomotive horns... almost enough to awaken the dead!
285/70-17 Toyo Open-Country A/T tyres (excellent on ice!).
Fully equipped as a motorsport recovery unit and licenced in the UK by the MSA.