Ram2500 V10 Overheating Problem

Whenever I put my 2000 V10 under load, driving uphill or towing my utility trailer, the temperture rises to 220 degrees and higher. The coolant rushes into the recovery tank until I start going downhill again or get rid of the trailer load. The Dealer installed new radiator, cap, water pump, thermostat, and hoses before I purchased it 10k miles ago.

There are no leaks in the system. No water in the oil. No moisture on cab floor or steam on windshield so heatercore is good, but I have to constantly add coolant. I've added about 5 gallons of liquid (coolant and/or water) over the past year so far.

I'm thinking bad fan clutch as fan rotational resistance is weak at high temps and stiffer when cool and was not replaced by the dealer when the other parts were installed.

Can anybody tell me if I'm on the right track?? I'd appreciate input. Thanks.