2008 GMC Envoy Owner's Manual - Page 104

AUTO (Automatic Four-Wheel Drive): This setting is ideal for use when road conditions are variable. When driving your vehicle in automatic four-wheel drive, the front axle is engaged, but the vehicle's power is sent to the rear wheels. When the vehicle senses a loss of traction, the system will automatically engage four-wheel drive. Driving in this mode results in slightly lower fuel economy than Two-Wheel High. 4 m (Four-Wheel High): This setting should be used when you need extra traction, such as on snowy or icy roads or in most off-road situations. This setting also engages your front axle to help drive your vehicle. 4 n (Four-Wheel Low): This setting also engages your front axle and delivers extra torque. It sends maximum power to all four wheels. You might choose this setting if you are driving off-road in deep sand, deep mud, and climbing or descending steep hills. {CAUTION: Shifting the transfer case to NEUTRAL can cause your vehicle to roll even if the transmission is in PARK (P). You or someone else could be seriously injured. Be sure to set the parking brake before placing the transfer case in NEUTRAL. See Parking Brake on page 2-33. NEUTRAL: Shift the vehicle's transfer case to NEUTRAL only when towing your vehicle. See Recreational Vehicle Towing on page 4-40 for more information. An indicator light in the knob will show you which position the transfer case is in. The indicator lights will come on briefly when you turn on the ignition and one will stay on. If the lights do not come on, you should take your vehicle to your dealer for service. An indicator light will flash while shifting the transfer case. It will stay on when the shift is complete. If for some reason the transfer case cannot make a requested shift, it will return to the last chosen setting. If the service Four-Wheel Drive Warning Light on the instrument panel cluster stays on, you should take your vehicle to your dealer for service. See Service Four-Wheel Drive Warning Light on page 3-47 for further information. 2-30