As stated above the tow/haul mode was designed for just this situation. On my 2016 Miramar, F-53 V-10, there is no red line on my tachometer. I’ve asked the Ford technicians about the tow/haul mode and the what seemed to be very high rpm’s while descending a steep grade.
He explained to me that this is engine is de-rated so much, there was no need to place a red line on the tach. He said if I use the engine as designed under normal driving conditions, I would never have a problem.
I too was concerned with the screaming of the engine while descending a steep mountain grade, 4500 rpm’s for several minutes. They assured me the engine was designed with this in mind!
I’ve observed all engine parameters available to me while descending grades and have noticed no changes to coolant temp, transmission temp or any other parameters. She just purrs like a kitten when she shifts back into low gear!
I’m fully loaded at approx 21,800 pounds while flat towing a Honda CR-V.
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