2008 GMC Sierra 1500 Pickup Owner's Manual - Page 147

Cruise Control When you apply your brakes, cruise control is turned off. If your vehicle has the StabiliTrak® system and begins to limit wheel spin while you are using cruise control, the cruise control will automatically disengage. See StabiliTrak® System on page 4-5. When road conditions allow you to safely use it again, you may turn the cruise control back on. {CAUTION: Cruise control can be dangerous where you cannot drive safely at a steady speed. So, do not use your cruise control on winding roads or in heavy traffic. Cruise control can be dangerous on slippery roads. On such roads, fast changes in tire traction can cause excessive wheel slip, and you could lose control. Do not use cruise control on slippery roads. With cruise control, you can maintain a speed of about 25 mph (40 km/h) or more without keeping your foot on the accelerator. This can really help on long trips. Cruise control does not work at speeds below about 25 mph (40 km/h). 3-11