1996 GMC Sonoma Owner's Manual - Page 67

Shift Light If you have a manual transmission, you have a SHIFT light. This light will show you when to shift to the next higher gear for best fuel economy. If you skip more than one gear when you downshift, you could lose control of your vehicle. And you could injure yourself or others. Don't shift down more than one gear when you downshift. If your vehicle has four-wheel drive and is equipped with a manual transmission, disregard the SHIFT light when the transfer case is in 4LO. SHIFT When this light comes on, you can shift to the next higher gear if weather, road and traffic conditions let you. For the best fuel economy, accelerate slowly and shift when the light comes on. While you accelerate, it is normal for the light to go on and off if you quickly change the position of the accelerator. Ignore the SHIFT light when you downshift. Locking Rear Axle If you have this feature, your rear axlecan give you additional traction on snow, mud, ice, sand or gravel. It works like a standard axle most of the time, but when one of the rear wheels has no traction and the other does, the locking feature will allow the wheel with traction to move the vehicle. 2-19