FLINT, Mich. (AP) — General Motors plans to spend $328 million to update a factory in Flint, Mich., to build the next generation of full-size pickup trucks.

The investment will pay for equipment to build the new Chevrolet Silverado and GMC Sierra pickup trucks, which are due in showrooms early in 2013.

The investment is part of $2 billion GM is spending to create or retain 4,000 jobs in eight states over the next 18 months.

At the Flint Assembly Plant, it will add about 150 jobs, said Dana Rouse, bargaining chairman for the United Auto Workers union local at the plant.

The plant currently employs 2,047 people and made 115,000 trucks last year. GM also makes pickups Silao, Mexico.

GM U.S. pickup truck sales were up about 13 percent through June compared with a year earlier, about the same increase as the overall U.S. market.

Separately, GM will start negotiations with the UAW on a new national contract on July 27. Both sides said at the Flint announcement that they want to work together to fairly pay employees yet keep company costs in check.