2003 GMC Sierra 1500 Pickup Owner's Manual - Page 121

Shift Speeds If your engine speed drops below 600 rpm, or if the engine is not running smoothly, you should downshift to the next lower gear. When operating on slippery surfaces, downshift at lower than normal vehicle speeds to prevent the tires from slipping. If you skip a gear when you downshift, you could lose control of your vehicle. You could injure yourself or others. Don't shift down more than one gear at a time when you downshift. In bench seat equipped vehicles, move the tallest beverage containers to the right cupholder to provide additional clearance for the shift lever. For vehicles equipped with a center console, the front cup holder pulls out and turns 180" to provide additional clearance between tall beverage containers and the shift lever. Do not allow the engine rpm to overspeed and enter the tachometer red lines. Engine overspeed occurs when downshifting, or descending a grade, at too high a vehicle speed. When going down steep grades, always select a gear at least one position lower than you would use on climbing a grade. This will allow the vehicle's engine to provide some braking and help to slow the vehicle as it goes down the grade. Monitor your vehicle speed, acceleration and engine rpm while applying the brakes as you go down the grade to ensure you have complete control over the vehicle. Shift Light - If you have a manual transmission, you may have a SHIFT light. This light will show you when to shift to the next higher gear for best fuel economy. When this light comes on, you can shift to the next higher gear if weather, road and traffic conditions allow. For the best fuel economy, accelerate slowly and shift when the light comes on. 2-34