You are only stating "hot" but without actually knowing the real temperatures the engine and trans are getting up to. Having the actual temperatures of both would be a big help in trying to diagnose the problem(s) or verifying that there really isn't a problem.
Get a ScanGauge, Ultra-Gauge or any one of the vast number of OBDII dongles and smartphone apps (like Torque) to monitor the engine and trans vitals.
Some factory dash gauges are really just three position idiot lights, cold, normal and above normal. A big heavy motorhome climbing a grade in the Summer very well may push the temp gauges above the "normal" sector of the gauges. Being able to see the actual numerical temp readings will tell you a lot more than the factory dash gauges.
Being a model year 2000 rig, do the trans cooling lines go into and out of the radiator then into a trans cooler or do they only go straight to the trans cooler? Some of the Super Duty pickups of that era didn't have the ATF flow routed through the radiator, something Ford corrected soon thereafter. Many owners of those trucks have updated them with later model radiators with the ATF cooling circuit for far better trans temp control while towing and hauling heavy loads.