2003 GMC Sierra 1500 Pickup Owner's Manual - Page 349

Tow/haul is designed to be most effective when the vehicle and trailer combined weight is at least 75% of the vehicle's Gross Combined Weight Rating (GCWR). See Weight of the Trailer later in the section. Tow/haul is most useful under the following driving conditions: When pulling a heavy trailer or a large or heavy load through rolling terrain. When pulling a heavy trailer or a large or heavy load in stop and go traffic. When pulling a heavy trailer or a large or heavy load in busy parking lots where improved low speed control of the vehicle is desired. Operating the vehicle in tow/haul when lightly loaded or with no trailer at all will not cause damage. However, there is no benefit to the selection of tow/haul when the vehicle is unloaded. Such a selection when unloaded may result in unpleasant engine and transmission driving characteristics and reduced fuel economy. Tow/haul is recommended only when pulling a heavy trailer or a large or heavy load. Weight of the Trailer How heavy can a trailer safely be? It depends on how you plan to use your rig. For example, speed, altitude, road grades, outside temperature and how much your vehicle is used to pull a trailer are all important. And, it can also depend on any special equipment that you have on your vehicle. Use one of the following charts to determine how much your vehicle can weigh, based upon your vehicle model and options. Maximum trailer weight is calculated assuming the driver and one passenger are in the tow vehicle and it has all the required trailering equipment. The weight of additional optional equipment, passengers and cargo in the tow vehicle must be subtracted from the maximum trailer weight. Above the 5,000 Ibs. (2 268 kg) trailer rating, the handlinghrailering suspension is required on C-1500 models and the handlinghrailering or off -road suspension is required on K-1500 models. 4-68