let me jump in with what I think this problem is.
does this unit "load up" when going up a hill or ramp, but idles well?
since you note the 230degree temp is in the transmission, also, and only after a less than 1 hour run, I think there is every reason to expect you have a bad torque converter (broken stator or stator blades).
Have you taken trans pressure readings and done a transmission stall test while watching the engine RPMs?
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