Truck isnt happy pulling trailer

[mcwilly]

I’ve got a question/concern about towing my trailer. I’ve got an ’06 F-150 SuperCrew with the 5.4 V8 and tow package. The trailer is a 19’ V-nose, tandem axle which I bought about a month ago. When I bought the trailer, I had to drive about an hour on the highway to get it home. From 0-50mph the truck didn’t seem to have any trouble pulling it, but when I got to about 60mph it wasn’t happy….downshifting constantly with ‘overdrive’ on. (trailer was empty). So I tried to keep it around 60mph as best I could. Granted I was driving into a pretty good head-wind.
So I ordered a Gryphon with custom 87 tow and 87 performance tunes. I haven’t got the custom tunes yet, but I had my first towing experience with the Gryphon this past weekend using the canned 87 tow tune and a full load in the trailer (four 4-wheelers, generator, two bicycles, gear bags and two hand-carry tool boxes…..oh, and I installed a rooftop A/C unit as well last week. My truck really struggled. Again, I had to stay around 60mph. With ‘overdrive’ off, it would run 60mph at around 2500rpm and stay at that speed pretty well, sometimes getting to 65mph at 26-2700rpm. With ‘overdrive’ on, of course it downshifted a lot more. BUT, with overdrive on, there was a gear (sweet spot) just below overdrive that it would sit at and run 60-65mph at around 1800-2000rpm which I tried to keep it at, but I couldn’t keep it there long with inclines. If/when it did shift to overdrive, the rpm’s would drop of course and I would get a loud drone sound. But it never stayed in overdrive longer than a few seconds.
I’ve seen a lot of threads where people are pulling heavier/larger trailers than mine and seem to be running better than where my truck is performing. My question is, is there a way to write the tune so that the truck will stay in the ‘sweet spot’ gear better instead of running too high in overdrive or too low when overdrive is off? Or does this sound typical for what I’m pulling? My ECT and Trans temp never went over 200 degrees. (Highest was around 195 degrees) Is there something I can do in the 'custom tune' section when in tow mode to make it better for now?
My truck is stock aside from a K&N filter with 20" wheels/tires. Planning on doing the Gotts mod this weekend.