The aerospace industry was first to use quick plastic forming with metal parts.
Until now it has been used only in low-volume applications on automobiles because it takes longer to produce body panels.
Other automakers, such as Ford Motor Co, will use the plastic-forming technology for the low-volume GT sports car.
The Malibu tailgate weighs 20 pounds. Had it been produced in steel, it would have required two separate stampings and weighed 39 pounds, says Alan Taub, executive director of GM's science laboratories.
What GM engineers have figured out is how to speed the process to produce more panels per day.
GM gave its system a test run on the 2001-03 Oldsmobile Aurora. But the Malibu is the first time that the process has been used in a high-volume vehicle.
Taub says GM can produce as many as 100,000 Malibu tailgates per year. Taub says GM spends around two minutes to produce each tailgate.
The same part made of steel could be stamped in a few seconds, but then it would have to be joined with a plastic outer structure, adding cost and complexity to the manufacturing process.
"We don't want to let our competition know how fast we are doing this because we've had a breakthrough there," says Taub.
"We are doing it faster than most people expected. Our patents are all going through. As far as we know, we own the process."
The GM system uses a special machine that heats a single sheet of aluminum to about 932 degrees.
The aluminum is moved in position under a die. Then hot air is used to blow the aluminum against the die where it forms the shape of a body panel. After that, the panel is cooled quickly. "We are not the first to use super plastic. Our breakthrough is aerospace super plastic at automotive volume and cost.
"You can't make this volume by the technique everyone else is using."