GMC 1999 Sierra 1500 Pickup Owner's Manual page 94

This is your shift pattern. Here's how to operate your transmission:
I
IC2287
L (Low Gear) (Overdrive Five-Speed Transmission Only)-Press the
clutch pedal and shift into L. Then, slowly let up on the clutch pedal as
you press the accelerator pedal. Shift into L only when the vehicle
speed is below 5 mph (8 km/h). If you try to shift into L at excessive
vehicle speeds, the shift lever will not move into the L position until
vehicle speed is reduced.
L is intended for heavy loads and
is not recommended for normal
driving.
1 (First Gear)-Press the clutch pedal and shift into 1. Then, slowly let
up on the clutch pedal as you press the accelerator pedal.
You can shift into 1 when you're going less than 20 mph (32 kmlh). If
you've come to a complete stop and it's hard to shift into 1, put the
shift lever in N (Neutral) and let up on the clutch. Press the clutch pedal
back down. Then shift into 1. If you try to shift into 1 at excessive
vehicle speeds, the shift lever will not move into the 1 position until
vehicle speed is reduced.
accelerator pedal and shift into 2. Then, slowly let up on the clutch
pedal as you press the accelerator pedal.
Higher Gears -Shift into the higher gears the same way you do for 2.
Slowly let up on the clutch pedal as you press the accelerator pedal.
2 (Second Gear)-Press the clutch pedal as you let up on the
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