So a few things with these transmissions.
1) The biggest culprit is there is a thermostatic valve on the cooler lines that will not open til 170*. Which could be an issue. I’ll link my video to the replacement of this valve at the bottom.
2) if everything is working properly you shouldn’t see anything over 200*. I’ve towed my 10,340lb loaded camper over some pretty steep grades in the southern Rockies at 100*+ OAT, never seen it over 200*. All of this was prior to Valve replacement.
The valve could be stuck partially closed/opened (all depending on how you look at life! LoL). They have been know to fail at all different time/mileage and blow transmissions up.
Easiest thing to do is pay the $103 and replace it. Super easy and you don’t lose a lot of fluid.
Also a trans temp general guide.
Picture of my set-up just because.
And videos as promised.
2018 2500 6.4 4x4 4.10 Amsoil SS 0w-40, Softopper
Black Rhino Armory 18x9 +12mm
Cooper St MAXX LT295/70R18
2016 Durango 5.7 AWD 3.07 Redline 5W-30 RP 10-48
1996 Nissan Altima 2.4 Amsoil SS 5W-30