Mountain Descent Gear Selection and the 'Same Gear' Rule
Mountain driving is one of the most hazardous conditions commercial drivers encounter. On long descents, the primary danger is brake fade — service brakes overheat from continuous application, reducing or eliminating stopping ability. The fundamental rule for mountain descents: select the same gear going down that you would use going up the same grade. If a hill requires 5th gear at 35 mph climbing, descend in 5th gear at or below 35 mph. This prevents runaway speeds that overwork the brakes. Before beginning any descent, slow to the appropriate speed BEFORE the grade, not during it. Once a loaded truck is moving too fast on a descent, attempting to slow it with service brakes may be too late. The pre-descent check: scan for posted warning signs indicating grade percentage and recommended truck speeds (common in western mountain states). A 6% grade for 10 miles at full load requires significant brake management. Grade steepness × distance × loaded weight × weather conditions all interact. Gravity acts constantly — even brief coast-and-brake cycles allow speed to build. Check your brakes at the top of the grade by applying them firmly and checking for full stopping response. If brakes feel soft or spongy before the descent, do not proceed until the problem is addressed. Brake adjustment and air pressure must be at normal operating parameters before mountain operations.