ARLINGTON, Texas (AP) _ Tension turned into relief Monday for 3,700 autoworkers who learned General Motors had picked their auto assembly plant over one in Michigan to make rear- wheel-drive cars. But there were no loud celebrations.

''You could hear a big sigh of relief. You could hear the rush,'' said Doug McMillan, an assembler, describing the reaction when plant manager Art Hester told workers they would be spared from GM's cost-cutting knife.

Four-thousand of their colleagues in Ypsilanti Township, Mich., will lose their jobs when that plant is closed next summer and its operations are shifted to Arlington.

''We're not going to celebrate because we feel bad for people who are losing their jobs,'' said Mike Seiler, shop chairman for UAW Local 276, which represents the Arlington workers.

''They are more or less our GM brothers and sisters,'' said Melvin McClendson, a job trainer at the plant.

On Dec. 18, GM had targeted the Arlington and Willow Run plants for closure as part of the giant automaker's restructuring. Both plants make big cars such as the Chevrolet Caprice and Cadillac Brougham, and GM said sales have been off so much that only one of the plants is needed.

General Motors said cost, location and the ages of the plants played a role in its decision. But union representatives said another factor may have been the willingness of the Arlington labor force to accept production changes.

Labor-management relations here are considered better than at most GM facilities. In 1986, the UAW local adopted a team concept in which workers learn each other's jobs.

When GM announced its restructuring, workers here voted to accept a more efficient 10-hour, four-day work week if the company asked for it.

''We have a good background of being flexible, of being productive,'' said Dave Perdue, president of the UAW local. ''The plant runs efficiently. We just sold ourselves.''

Now Arlington will need to hire 1,000 more workers and add a shift to take on production from the Willow Run plant.

''It looks like I'm going to make my retirement,'' said John McNamara, who has put in 24 years at the plant and needs six more to retire.