Towing through mountains

Also, do not worry too much about holding speed. Every time a see someone with a 15000lb 5vr going over a pass at 80mph, I am thankful I decided to buy my truck new, rather than used.
Just downshift as needed, get into the right hand lane and maintain a reasonable speed, say 45-65 depending on how steep the grade is.
On the way down, let the tranny/exhaust brake do most of the work.

I use the tow/haul going up and down long grades, I do not leave it in cruise control, I have heard bad things about vehicles jumping out of cruise because of to much pressure on the transmission... Also If the pedometer start to sound I back off till it quits, your only hurting your engine if you keep pushing it past that point of no return ...

I going down the hill useing a lower gear than I went up the hill, not applying the brakes hard (never ever hold down on your brakes hard for length of time you will loose them going down a 6 percent grade). I Only apply my brakes enough to keep me at a slow speed an not over rev my engine or picking up any great ampunt of speed ...

Some of the grades out here in the western United States are 6 percent at 10, 15 and at times miles longer... If you keep hitting your brakes every few seconds or really hard you will loose them, trust me, I've seen it...

Do not be sacred of any of the mountain passes out here, if you use you head, think about what your doing you will be fine ...

Safe travels

Tow haul is a good start. If it seems to be bogging down or having a hard time keeping speed then you can experiment with downshifting. Hard to say without your trailer weight and driving it. If your Ford is stock then tow haul should do it. If you have a programmer or anything then it gets more complicated.

set cruise control go into tow haul and let the engine/transmission decide what to do on the way up. and if cruise works going down (which the allison on late models do) turn on exhaust brake and set cruise for desired downhill speed and let it do it's work to hold you on the downhill side.

sure, you could use the manual transmission mode, turn off cruise, but I've never found that to be an advantage, if anything a disadvantage. I just let cruise control do it's job. It's been very very very seldom where cruise wouldn't hold the speed I wanted, or very close to it.

Just floor it.

How you work it depends on the vehicle and the load and the speed. I know nothing about your specific rig or the programming of the engine and transmission computers. I also do not know anything about your engine cooling system. I can only tell you what works for me.

I've a diesel with an auto transmission, too. The engine also has a mechanically driven water pump. I have found that sport mode (what you call tow/haul mode on your truck) works better when towing than the normal mode, which is designed to maximize fuel economy. I suspect you'll find the same. If the terrain is flat, I'll often leave it in normal anyway, but put it in sport/tow/haul for extra engine braking or accelerating power or climbing gentle slopes.

But when the going gets rough, the road gets steep, and the climb gets long, or when the downgrade calls for engine braking to save the wheel brakes, I'll go to manual gear selection and keep those revs up, both for the power and engine braking, but also to make sure the water pump is going full blast to keep engine temps down.

It's lovely having an auto transmission to handle all those decisions. Makes driving so much easier. BUT, and it's a big but, there are times when I want to get all the performance possible, and those computers are just not programmed to provide that.

Currently the Allison transmission takes care of it for me. I always drive with tow/haul on and when going down a steep hill I set the cruise to 5-10 under the speed limit or recommendation for trucks and only have to touch the brake-hard as previously stated above-if some idiot pulls in front of me then slows down.

Love that Allison.

The tow mode is nice but I do prefer the manual mode particularly on the downhill side. Going uphill I can make it shift down one with a twitch of the foot. I do miss a full manual transmission sometimes but it is not too difficult to make the Alisson behave somewhat like a manual.

Figure what speed you want to try to maintain, cruise off tow/haul on and manually shift gears as needed to hold speed. Going back down the back side, let the transmission help hold your speed down. If braking is necessary, apply brakes hard to reduce speed and then get off them DO NOT ride the brakes.