I have a Scangauge on my 2005 Fleetwood 39S. I'm running synthetic in the transmission. It's interesting the watch the Scangauge. It will show the air intake temperature - as it goes up, so does the transmission temperature. On a flat highway with an air temp of 86 at about 62 - 63 mph, my transmission temp is more around 180. I'm not saying yours is too high, but mine is cooler. I've very seldom seen mine hit 200; I think the highest I've seen in the mountains in Canada was 206. I'm pulling a Jeep Wrangle and travel with a full tank of water since we never know where we'll stop.
Bill