General Motors will invest US$61m to bring its idled Spring Hill (Tenn.) assembly plant back to life as a flexible manufacturing facility capable of building any GM car or crossover based on customer demand or manufacturing need.

The investment will create 594 hourly jobs and 91 salaried positions for the flexible operation scheduled to begin with the Chevrolet Equinox in the second half of 2012.

The additional production will supplement Equinox production in Canada, the main assembly sites of the midsize crossover vehicle and its sibling the GMC Terrain.

US sales of Equinox were up 18% in October and GM has increased production three times since it went into production in 2009.

GM also announced Monday a second investment of $183m for future midsize vehicles to be built at Spring Hill, located about 40 miles south of Nashville. Timing was not announced, but that investment is expected to create an additional 1,090 hourly and 106 salaried positions.

The potential for Spring Hill's future role was discussed as a part of negotiations for a four-year national labour agreement with the UAW ratified in October.

Equinox production is only the start for Spring Hill Flex. GM says that operators will be capable of building a variety of products on a range of platforms - covering for plants being retooled for new products and also allowing real-time reaction to sales spikes in a given car or crossover.

Spring Hill powertrain and stamping operations, part of the integrated complex that was the home to the former Saturn brand from 1990 to 2007 and the Chevrolet Traverse large crossover into 2009, are still operating.