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I doubt it is really a 30 degree incline. A 30 degree incline is a 57% grade! If the machine weighs 8 tons and the gooseneck weighs 2 tons, and the truck weighs 3 tons, we have 13 tons trying to go up the hill. The amount of force parallel to the direction of travel will be 13 * sine(30) or 6.5 tons. If we assume 10% of the loaded trailer weight is on the gooseneck (on the flat), then the truck exerts a force of (3 * 0.1 * 10) * cosine(30) normal to the road, or 3.46 tons. If we assume a 4WD truck with the transfer case locked, and we optimistically hope for a coefficient of friction of 1.0 between the tires and the pavement, then the maximum tractive force the truck can exert on a 30 degree slope is 3.46 tons. With 3.46 tons pulling up, and 6.5 tons pulling back, the answer is that you have no chance at all of pulling the trailer up the hill. The tires will slip on the pavement. It doesn't matter how much power you have. Let's refigure for a 30% grade (still really steep). This is a 17 degree slope. Force pulling parallel to the road is 13 sin (17) or 3.7 tons. Force normal to the pavement is 4 * cos(17) or 3.8 tons. At a coefficient of friction of 0.5 the truck can exert a maximum of 1.9 tons of tractive effort. You need a coefficient of friction of almost 1.0. Still can't do it, the tires will spin hopelessly. Try again with a 20% grade. Even that looks really steep, most "mountain roads" are around 10 or 11 percent. A 20% grade is a slope of 11 degrees. Force parallel to the road is 13 * sin(11) or 2.5 tons. Force normal to the road is 4*cos(11) or 3.9 tons. You need a coefficient of friction of 0.64 or higher or the tires will spin. Not very likely -- a figure of 0.5 is about the limit to expect. The moral of the story is that pulling trailers up steep grades is very difficult -- the weight of the load does not help in developing tractive force, but instead parasitically pulls back on the whole works. If the dozer were on a flatbed truck, and thus helping to load the driving wheels, that works a whole lot better. The math is pretty inescapable. It ain't gonna work, regardless of whether it is safe or not, unless the driveway is actually more like a 10 percent grade.
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