What you experienced is a classic fan clutch going bad symptom.
It will run just fine...until it needs more CFM
On that, the thermal system is designed to run at a preset temp range (thermostat, fan cutch, etc).
As you demand more cooling...AKA towing, hauling, going up an incline, speeding up, etc...the cooling system will increase until al of their component/sub-systems reach their max performance capacity...then the temp will raise until the temp reaches preset safety temp points
Then the ECU will drop off of power mode and start to go into ever lower limp modes...if you continued...you would have experienced it going into limp modes, until it would only allow crawling
OEM fan clutches couple water pump shaft RPMs around 40%-50%. HD and SD couples around 80%-90% or more water pump shaft RPM’s. The main diff between HD & SD is in the bearings, shaft clip, etc...to keep it from taking off like an airplane into the radiator
It is about time anyway. Fan clutches d wear out. F you go with a new one...suggest only getting a severe duty
ROAR will be significant, so beware and don’t get startled...a very good thing to have almost twice the CFM of an OEM fan clutch...
I like TRW fan clutches and hope they haven’t gone bean counter management of decreasing quality for a few more bucks profit...
Almost forgot...let the new fan clutch sit over 24 hours with the nose “UP”...has to do with settling the coupling fluid internal to the clutch
(Edit)....dash temp gauge drops like a rock once my fan clutch kicks in
