2003 GMC Sierra 1500 Pickup Owner's Manual - Page 117

If your vehicle has both tow/haul and overdrive disable tap the button once to enable or disable tow/haul, and press and hold the button to enable or disable overdrive disable. Manual Transmission Operation Five-Speed (VORTEC 6000 V8 Engine) FIRST (1): Press the clutch pedal and shift into FIRST (1). Then, slowly let up on the clutch pedal as you press the accelerator pedal. Shiftinto FIRST (1) only when the vehicle is below 5 mph (8 km/h). If you try to shift down into FIRST (1) at excessive vehicle speeds, the shift lever will not move into FIRST (1) until vehicle speed is reduced. SECOND (2): Press the clutch pedal and shift into SECOND (2). Then, slowly let up on the clutch pedal as you press the accelerator pedal. You can shift into SECOND (2) when you're going less than 20 mph (32 km/h). If you've come to a complete stop and it's hard to shift into SECOND (2), put the shift lever into NEUTRAL and let up on the clutch. Press the clutch pedal back down. Then shift into SECOND (2). If you try to downshift into SECOND (2) at excessive vehicle speeds, the shift lever will not move into the SECOND (2) position until the vehicle speed is reduced. FIRST (1) is intended only for heavy loads or trailer towing and is not recommended for normal driving. During the first 500 miles (805 km) of vehicle use, start your vehicle moving in FIRST (1). This allows clutch components to break-in properly. 3: THIRD ( ) Press the clutch pedal and shift into THIRD (3). Then, slowly let up on the clutch pedal as you press the accelerator pedal. FOURTH (4) and FIFTH ( ) Shift into the higher 5: forward gears the same way you do for THIRD (3). Slowly let up on the clutch pedal as you press the accelerator pedal. 2-30