1998 GMC Sonoma Owner's Manual - Page 94

Shifting from 2HI 4HI to 4LO or To shift from 2Hl or 4H1 to 4L0, the vehicle must be stopped or moving less than 3 mph (4.8 k d h ) with the transmission in NEUTRAL (Nj in vehicles equipped with an automatic transmission. The clutch pedal must be engaged on vehicles equipped with a manual transmission. The preferred method for shifting into 4LO is to have your vehicle moving 1 to 2 mph (1.6 to 3.2 k d h ) . Press and release the 4LO switch.You must wait for the 4LO indicator light to stop flashing and remain illuminated before shifting your transmission into gear or releasing the clutch pedal. If the 4LO switch is pressed when your vehicle is in gear and/or moving, the 4LO indicator light will flash for 30 seconds and not complete the shift unless your vehicle is moving slower than 3 mph (4.8 km/h) and the transmission is in NEUTRAL (Nj or the clutch pedal is engaged. On automatic transmission equipped vehicles, if your transfer case does not shift into 4L0, your transmission indicator switch may require adjustment. With your transmission in NEUTRAL (Nj, press and release the 4LO switch. While the 4LO indicator light is flashing, shift your transmission into PARK (P). Wait until the 4LO irldicator light stays on before shifting your transmission into gear. This will get you into 4L0, but you should take your vehicle in for service to restore normal operation. Shifting from 4LO to 4HI or 2HI To shift from 4LO to4HI or 2H1, your vehicle must be stopped or moving less than 3 mph (4.8 kmh) with the transmission in NEUTRAL (N) or the clutch pedal engaged. The preferred method for shifting out of 4LO is to have your vehicle moving 1 to 2 mph (1.6 to 3.2 kmdh). Press and release the 4HI switch. You must wait for the 4HT indicator light to stop flashing and remain illuminated before shifting your transmission into gear or releasing the clutch pedal. If the 4HI switch is pressed when your vehicle is in gear and/or moving, the 4HI indicator light will flash for 30 seconds but not complete the shift unless the vehicle is moving slower than 3 mph (4.8 km/h) and the transmission is in NEUTRAL (N) or the clutch pedal engaged. 2-30