When Saturn Corp. workers granted strike authorization to UAW Local 1853 in July, one issue in dispute was how much of a bonus 7,200 workers should receive for the second quarter. The UAW says the payment, which hinges on the plant achieving production, quality and training targets, should be about $1,400 per person. The company wants to pay $390.

But the larger issue is whether the labor-management partnership that has defined Saturn can survive General Motors Corp.'s push to use outside suppliers to build bigger chunks of future vehicles.

Michael Bennett, bargaining chairman for Local 1853, says GM officials will decide in the next 30 days which suppliers will build crucial parts of anew sport/utility vehicle Saturn wants to build to compete against the Toyota RAV4 and Honda CR-V.

Saturn is much more integrated than most GM assembly plants. Stampings, plastic side body panels, engines, even its engine blocks are cast on site.

That's not compatible with the vision GM executives have of the manufacturing process of the 21st century.

Some of them have told Mr. Bennett that on the new SUV everything from the instrument panel and cockpit, doors, stampings and other injection-molded parts will be built in modules by outside suppliers.

If the same approach is used on the next generation of Saturn's basic small cars, the UAW worries that some of its 7,200 jobs in Spring Hill could disappear.

"They've told us if we don't want to do it that way, they can build it in Lansing," Mr. Bennett says. "We're not about uncompetitive work practices. Here we are trying to implement lean manufacturing principles, and they want to take work away from us."

Privately, some Saturn managers share Mr. Bennett's frustration, but they also wince at the prospect of Saturn's cooperative spirit being jolted by its first strike.

Others close to the situation say Mr. Bennett would not be taking this situation to the brink without the leverage that the two-month-old walkouts in Flint provide him.

"With respect to a commitment to preserving UAW jobs, our track record speaks for itself," says Saturn spokesman Greg Martin.