2008 GMC Acadia Owner's Manual - Page 311

Turn Signals When Towing a Trailer When you tow a trailer, your vehicle may need a different turn signal flasher and/or extra wiring. Check with your dealer/retailer. The arrows on your instrument panel will flash whenever you signal a turn or lane change. Properly hooked up, the trailer lamps will also flash, telling other drivers you're about to turn, change lanes or stop. When towing a trailer, the arrows on your instrument panel will flash for turns even if the bulbs on the trailer are burned out. Thus, you may think drivers behind you are seeing your signal when they are not. It is important to check occasionally to be sure the trailer bulbs are still working. Driving on Grades Your vehicle is designed primarily as a passenger and load carrying vehicle. If you tow a trailer, your vehicle will require more frequent maintenance due to the additional load. Because of the added load of the trailer, your vehicle's engine may overheat on hot days, when going up a long or steep grade with a trailer. If the engine coolant temperature gage indicates overheating, turn off the air conditioning to reduce engine load, pull off the road and stop in a safe spot. Reduce speed and shift to a lower gear before you start down a long or steep downgrade. If you do not shift down, you might have to use your brakes so much that they would get hot and no longer work well. On a long uphill grade, shift down and reduce your speed to around 55 mph (88 km/h) to reduce the possibility of the engine and the transmission overheating. 4-39