And, Ford's torque control is going to get in the way if you go too high. Bill posted about this somewhere a long time back and I can't really think of a good "search string" to find it. Maybe if you search on all posts by "Power Hungry" and "gears" you may get lucky?
At any rate, if you put the gearing too high. the PCM won't see the need for power and will limit what you can get (at least that is what I understand).
Bill also published an Excel spreadsheet "RPM vs MPH calculator.xls", recently that you may be able to find pretty quickly if you look for it.
Personally, I would not go above 4.10.
- Jack
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2024 F150 Platinum SCrew 3.5L PowerBoost FX4, Peragon Tonneau Cover, LineX Bed, 35% Window Tint on All Sides and Rear, Full Nose Paint Protection Film, Husky Mud Guards, Lasfit Floor Liners, VIOFO Dash Cam