I was towing my daughters horses to a barrel race in Perry, Ga and back to Mississippi but noticed when going up a hill or really getting on it, it sounded like a fan kicked on in the engine compartment? Is there a transmission fan or something that comes on when under a heavy load? Or what am I hearing. And almost feels like I am losing some boost when it comes on?

Its a stock e99 f350

 

cooling fan locking up.

 

That would be your fan clutch. It engages when the coolant temps get around 215 degrees. Completely normal.

 

Thanks I don't hear it that much had me worrying something was wrong.