GMC Pickups 101: Busting Myths

Auto makers have been concerned with aerodynamics for almost a century. But when most people think about drag coefficients or sweeping curves it’s an exotic sports car or a futuristic hybrid that comes to mind. The last thing that they would think of is a pickup truck. Pickups are associated with words like durable, utilitarian and workhorse. But the days of dollar a gallon gas are over, and to get the job done a pickup needs a large and powerful engine. Pickup owners may talk about cargo capacity and tow ratings, but if they could get all that and save at the pumps too, that would be a game changer.

Understanding this, General Motors has spent more than a little time in the wind tunnel developing their latest full size GMC pickup trucks. But not just any old wind tunnel would do. GM’s wind tunnel is 750 feet long and uses a fan that puts out the equivalent of 4,500 horsepower. That’s about six NASCAR engines put together.

What they discovered is that by making a few subtle adjustments they could dramatically improve gas mileage and make the truck quieter, without sacrificing any of the rugged usability that built their reputation. The end result is a truck with highest in its class fuel economy despite sticking with a six speed automatic transmission.

The new Chevy trucks feature a front air dam that directs air away from the body as well as ducts behind the grill to stop air buffeting around in the trucks cavities. They also noted a lot of turbulence between the cab and the bed which was addressed with new sealing. Even the top of the tailgate and high mounted brake light have been tweaked for aerodynamic efficiency.

The GM testing also put to the test a lot of myths surrounding pickup trucks, particularly concerning the tailgate. It has long been believed that removing the tailgate, or replacing it with a net would increase performance and fuel economy by making the truck less wind resistant. The results told a different story. Lowering or removing the tailgate had the reverse effect. Airflow over the cab actually pushes the truck, which does not happen without a tailgate. Replacing the tailgate with a net makes matters even worse as the loss of aerodynamic efficiency is compounded by additional drag.

The GM team also looked at how aftermarket accessories impacted the trucks aerodynamics. They found that many play havoc with performance; the biggest culprits being bug deflectors and wider tires. Others, such as molded running boards improve performance. The final piece of advice from GM engineers regarded tonneau covers. Soft is better than hard here as the softer covers adapt to airflow, creating less resistance.