If the tractor of Problem 6.7 is operated down a 4% slope and the rolling resistance is 80 lb/ton, determine the maximum external pull by the tractor in each of the five gears. Problem 6.7 A pneumatic-tired tractor with a 300-hp engine has a maximum speed of 3.6 mph in first gear. a. Determine the maximum rimpull of the tractor in each of the indicated gears if the engine efficiency is 92%. b. The tractor weighs 29.2 tons. It is operated over a natn roan navmg a slope of +2.0% and a rolling resistance of 84 lb/ton. Determine the maximum external pull by the tractor in each of five gears.