DETROIT - General Motors is giving its big pickups a much-needed makeover.

The company unveiled new versions of its top-selling Chevrolet Silverado and GMC Sierra on Thursday, aiming to get them to showrooms by late spring or early summer.

The timing is good. The 2014 models roll into a market where truck sales are growing after a five-year slump. And GM's current trucks are dated, hurting sales. Those trucks, last revamped in 2007, are the oldest on the market and have fallen behind newer models from Ford and Chrysler.

GM says the revamped Silverados and Sierras, delayed by the company's trip through bankruptcy protection in 2009, should put the company back in front.

The trucks look a little more aggressive and aerodynamic. They will have quieter cabs and updated steering, suspensions, and brakes, GM says.

The automaker did not disclose gas mileage and pricing of the trucks, but GM North American president Mark Reuss says customers will be surprised by the prices. He says the trucks are 200 pounds lighter than Ford and Chrysler competitors, which will help boost gas mileage.

The trucks should close the gap with Ford and Ram, especially if the engines are more powerful and efficient, said Jeff Schuster, senior vice president of forecasting for LMC Automotive, a Detroit-area industry consulting firm.

He said he was impressed by GM's attention to detail. For example, there's a step built into the rear bumper to gain access to the bed. And the doors fit into recesses in the body to make the trucks quieter.

GM, which has been building Chevy trucks for 95 years, says the new models should hit the market at a good time.

The economy is improving and pickups are starting to sell again. The housing industry, which has a direct relationship to pickup sales, is strengthening and should be in even better shape by springtime, when the weather gets nicer. Plus, trucks now on the roads are aging and need to be replaced. The average age of a pickup in the United States is 10.4 years, GM says.

GM is having a tough time selling its current trucks against Ford's F-150 and Chrysler's revamped Ram. Sales for full-size GM pickups fell 8 percent last month, while competitors saw increases. At the end of November, GM had enough trucks on dealer lots to supply them for 139 days of sales.