Dear Tom and Ray:
I tow a 6,500-pound travel trailer with a 2009 GMC Sierra. The truck has a 5.6-liter engine with a trailer-towing package. My friends tell me not to tow with the cruise control on. I can find nothing in the owner's manual pertaining to this. Is it safe to tow with the cruise control on?
RAY: I don't see why not. All the cruise control does is keep your speed steady. And if the vehicle is otherwise capable of towing the load, it shouldn't have an adverse effect on anything.
TOM: The only exception would be if you're towing in a hilly area. In that case, in order to keep the truck at a precise, constant speed, the cruise control may force the automatic transmission to "hunt" for the right gear, and might go back and forth between gears quite frequently.
RAY: That's something that happens anyway in hilly driving, even without cruise control. It's not particularly harmful; it's just annoying.
TOM: If you were driving without cruise control in those hills, you might have a little more influence over the hunting. You might back off the gas pedal in certain situations, or downshift the transmission temporarily to stop the hunting.
RAY: But you can downshift with the cruise control on, too, if you notice hunting and it bothers you.
TOM: Just make sure you follow all the other towing recommendations the manufacturer makes, which probably include turning the overdrive off when towing, and strapping on two pairs of Depends before you head out with 6,500 pounds kissing your rear bumper.
RAY: But I'd say there's no real problem with using cruise control while towing, especially for normal highway driving, Russell.