Jtnuge: Some random observations since you originated the thread.
1. From cold on a 36-deg morning running 75+ on the freeway the gage barely moved from a small bar at the C-end. However, when I exited the freeway, the bar rose into the normal (almost 1/2 way) range within minutes - almost as if the thermostat had finally opened.
2. Similar 36-deg morning running on local/city streets it took about 20-min to slowly progress into the normal range, or about 2x as long as usual.
3. Yesterday at 50-deg, it acted normally.
Nothing scientific, but I am assuming the freeway at low temp provided more than enough natural cooling for the trans. Not sure where the temp sensor is located but if it is on the trans cooler outlet then it would help explain the delayed readings.