In a response to warnings that some full-sized vans roll over during evasive maneuvers, GM is adding stability control to two full-sized vans for the 2005 model year. Beginning in November, stability control will appear on the short-wheelbase, 12-passenger 2005 Chevrolet Express G3500 and GMC Savana G3500, according to Automotive News. Those 2005 vehicles assembled before November will not have the feature.GM will spread out the price increase when the feature is added as standard equipment. It will hike prices several times during the 2005 model year and possibly the 2006 model year.Stability control works in combination with the electronic engine throttle, antilock brakes and steering wheel input. GM markets the system as Stabilitrak. Stabilitrak adjusts engine speed and modulates individual brakes during evasive maneuvers so the driver has less risk of rollover. The auto industry's 15-passenger, full-sized vans have been the target of warnings from the National Highway Traffic Safety Administration. Problems are more likely if a vehicle is fully occupied.