Hi,
It is a long question to ask "What should my maximum fluid temp be?"
I read a poster on a wall in a transmission shop. IT basically stated that 300F trans fluid was good for something like 100 miles, or maybe it said 10 miles. 275 for 100 miles, and 250 for something like 5,000 miles between changes. 230F fluid is good for a somewhat normal 15,000 mile service life.
I prefer to keep my transmission fluid below 210F most of the time, with short duration of 230F while climbing a mountain. If it gets close to 230F, I would slow down, rather than overheat the transmission.
My 97 Ford F-53 chassis and 30' motorhome never went over about 200 on level ground, and up to about 225 F on a long mountain grade at 45 MPH in 2 gear (of 4). I have a 460" engine, old school compared to your V10 that can rev up much higher with much smaller pistons and shorter stroke that can rev up to 4,000 - 4,500 with ease.
I also tow a 4,000 pound car. My 30' RV is only about 16,500 pounds, so I am a bit lighter than yours. However my 460" engine is only rated at 225 HP at 3,600 RPM, much less than the 362 HP that your engine is rated at.
If your transmission is running over 210F on level ground, then I suggest a larger transmission cooler. However you do want (or need) to keep the transmission fluid over about 180F - even in winter. Moisture in the transmission fluid is driven out by running at 200F - it will boil all that water away. Keeping the fluid below 150F - such as short runs to work in the winter time, and moisture will not boil away, and can be bad.
Fred.
