Grade - According TM 20-205, Dictionary of United States Army Terms, 18 January 1944, a"slope of a hill, road, or railroad."
Steep downgrades. Make sure that your lowest gear is engaged before attempting to drive down any grade over 30 percent.
Steep upgrades. Before driving up a steep grade, also make sure that the lowest gear is engaged. If the traction is poor you may have to use a winch. If you truck has no winch, you may get help from one that has. In the absence of a winch, ordinary block and tackle may be used.