So, I originally had a 2014 Ram 3500 SRW deleted, with Cummins/Aisin that had duel radiators. When towing my coolant temps always stayed between 190-200, when towing our 5th wheel, approx 14k.

We decided to upgrade to a dually and traded for a 2015 Ram Cummins/68RE combo, undeleted. I screwed up major and assumed the truck came with Aisin, and a few days later discovered my mistake.

Anyway, now when pulling my fifth wheel, with my new truck. My coolant temp is approaching low 220s on hard climbs. I replaced my thermostat and had a coolant flush done, which didn't really help. We sold our 5th wheel in Grand Junction and loaded our stuff in a 6x12 uhaul trailer. When driving with the Uhaul trailer from Grand Junction to Denver, when pulling up the hills. I easily hit 214-218, with a few low 220s. The uhaul trailer can't be more than 3k in weight. But the truck temp was high, I felt like. Outside air temp was 50-60 degrees. New Thermostat is a 190. My fan is kicking on when I get to around 220, so that's good, but not sure about the temps I'm seeing? Can't imagine doing the same run at 90 or 100 outside temps.

Also one other tidbit to add, the truck came with a diesel fuel heater, like you would use on a semi? The unit is mounted back by the fuel tank, under the bed. It uses coolant as part of the system. So not sure if the added run of coolant lines could add issues for the cooling system? Just trying to figure out my engine temps. We are headed to MN to pickup our new toy hauler that will be even bigger and heavier than our last 5th wheel. Hence the switch to the DRW.

Any help or input would be appreciated.