2010 GMC Savana 2500 Cargo Owner's Manual - Page 257

If the loaded trailer being pulled will weigh more than 5,000 lbs (2 270 kg), be sure to use a properly mounted weight-distributing hitch and sway control of the proper size. This equipment is very important for proper vehicle loading and good handling when driving. Always use a sway control if the trailer will weigh more than these limits. Ask a hitch dealer about sway controls. Will any holes need to be made in the body of the vehicle when a trailer hitch is installed? If using the wiring provided with the factory-installed trailering package, no holes need to be made in the body of the vehicle. However, if an aftermarket hitch is installed, holes may need to be made in the body. If holes are made in the body, then be sure to seal the holes later when the hitch is removed. If the holes are not sealed, deadly carbon monoxide (CO) from the engine's exhaust can get into the vehicle as well as dirt and water. See "Carbon Monoxide" under Engine Exhaust on page 3-38. Tow/Haul Mode Pressing this button at the end of the shift lever turns on and off the tow/haul mode. This indicator light on the instrument panel cluster comes on when the tow/haul mode is on. Safety Chains Always attach chains between the vehicle and the trailer. Cross the safety chains under the tongue of the trailer to help prevent the tongue from contacting the road if it becomes separated from the hitch. Always leave just enough slack so the rig can turn. Never allow safety chains to drag on the ground. Tow/Haul is a feature that assists when pulling a heavy trailer or a large or heavy load. See Tow/Haul Mode on page 3-33 for more information. 5-33