Alright... this is kinda' stupid, but it still should have worked. I was in East Coast USA stock. I went into the world editor to drain the water plane down to 0 meters so that I could drive out to the islands on the dry water beds, and drive through the dry creek beds under the bridges. You know... just for fun. I also for some strange reason discovered I could drive across the water (out past the boundary square of the map itself).. odd... but okay, not complaining. What I noticed though was the truck red lined at 55mph or so and wouldn't upshift, like it normally does on proper dry land. Even though the ocean bed is dry, does the game sense that water ought to be there by default, and therefore is not allowing the truck to shift past 1st or 2nd gear? I can't honestly tell which gear it is in since automatic transmissions shift so subtly. (I can't even hear the shift points in my own automatic trans cars in real life, so even harder to hear them in the game). Is their a UI app that reads out the actual gear that an auto-transmission car is in at any given time, or no one has done that yet? I searched, and couldn't find.
55mph is top of 1st gear on the stock truck.. the automatic transmission does not shift up a gear if the wheels are slipping and thus it might have thought the wheels were slipping the whole time not allowing an upshift.
Okay, thank you. I realized after you said that, that the truck was still driving across wet sand/rock. By lowering water to 0m earth to 0m, the water was still sloshing up above the rock level. Even just lowering the water another -0.6m below was enough to dry things out, so that the truck could upshift. It was really rather interesting what a difference that small detail made. I'm guessing if one doesn't mess with the default water plane and earth settings, and doesn't drive so close to the water edge, that this will seldom ever be a noticeable problem.
The problem is neither old nor modern ATs have the ability to determine wheelspin if all wheels are at the same speed, however, BeamNG does that incorrectly.