Tennessee Pass—1985 Rolling over the very top of Tennessee Pass after helping an eastbound Rio Grande freight up the 3% grade out of Minturn are four SD40T-2 Tunnel Motors—the engineer notching up the dynamics as they enter east portal of Tennessee Pass tunnel on July 9, 1985. All too soon, they’ll be needed again to wrangle more tonnage up the 10,221-foot pass over the Continental Divide in Colorado.