DETROIT -- Because Ford needs to keep up with Americans' appetite for new cars and trucks, the company will add 200,000 vehicles of annual capacity, and get another 40,000 vehicles by cutting the traditional two-week summer shutdown in half.Getting more production from fewer plants reduces manufacturing costs and Ford's break-even point, but it's only possible with flexible labor contracts with its unions and with equipment that can run almost around the clock with little down time for maintenance.The company expanded its annual North American capacity by 400,000 vehicles last year, a move that has helped it keep pace with a 13 percent increase in its U.S. sales for the first four months of this year."That's more capacity (added) than (I've seen) in my 35 years in the business, that is being added in a very short period of time," said Jim Tetreault, head of Ford North America manufacturing. "We have F-Series plants that are going to produce 320,000 annually."Plants in Flat Rock, Mich.; Chicago; and Kansas City, Mo., have increased production of Explorer, Fusion and F-Series pickups.As a result, Ford will add 3,500 jobs this year - part of the commitment in the 2011 UAW contract for 12,000 additional workers by 2015. Most will be hired for a second shift at Flat Rock to make more Fusions and in Kansas City to make more F-150s and the new Transit commercial van. Tetreault said Ford has almost reached 75 percent of its jobs commitment."Ten years ago, we ran plants on two 8-hour shifts a day, and when times were good we ran 10-hour shifts and eight hours on Saturday," Tetreault said, but 58-hour weeks put a lot of wear and tear on people and equipment, not to mention substantial overtime in their checks.Now Ford uses three or even four crews to keep a plant running 120 hours a week. Tetreault said powertrain plants can run 141 hours a week."We had to learn to design production equipment that could run that many hours a week," he said.Workers will have less time off this summer with 20 of 31 plants closing for one week. Those where production stops for a second week need time for model changeover, including next-generation pickups and the new Mustang.General Motors is launching several key vehicles, but doesn't rely on traditional summer shutdowns to prepare plants. Instead it uses "rolling changeovers" that keep the lines running, Mark Reuss, president of GM North America, said Monday.To meet demand of popular products including some Jeeps and the Viper, Chrysler's Toledo North facility in Ohio and its Jefferson North and Conner Avenue facilities in Detroit will not take any time off in July, according to spokeswoman Jodi Tinson. Other plants will only have a single week off. Engine, stamping and all but one transmission plant will work without a break as well.