I'm gonna respectfully disagree with you Bennett.
With a heavy load like a boat, you should turn off O/D and drive 45 in all cases except MAYBE if you are on a long trip, no stops, on a flat highway with no traffic and you are driving 55mph.
Otherwise that computerized transmission will be constantly going in and out of overdrive and that will cause it to overheat.

And with O/D off, there is engine breaking when you let off the gas.

Of course, if you are driving 55 or higher without O/D, you will get really shytty gas mileage and probably overheat...


And I'm pretty sure that transmission "remembers" and "learns" shift points...

I'd disagree with me too......except that's what happened in my case, within the 1st year with the Explorer. It over heated and I took it back to the dealer.
Dealer manager told me to keep OD on and all would be fine. His son and I work at same company, and he had the same issue/ same outcome.

Defies the usual logic, but the vehicle never overheated again, and I've been towing the same route. Most, but not all is highway, 55 mph, and I have to slow down if it drifts to higher speed......

No matter, just interesting story, and something to check out when towing on highway.