Two Jeep plants and the facility assembling the SRT Viper will remain open through the summer, Chrysler says today.

The auto maker says most of its North American plants will have brief summer shutdowns. The exceptions are the Jefferson North Assembly Plant in Detroit, which produces the Jeep Grand Cherokee and Dodge Durango; Toledo (OH) North, home of the Jeep Wrangler; and Conner Ave. Assembly in Detroit, which builds the low-volume Viper supercar.

The Grand Cherokee and Wrangler are keys to long-term international success for the Fiat-Chrysler partnership. The Grand Cherokee is new ’14 but both are sold worldwide as CEO Sergio Marchionne boosts Jeep’s global presence.

Viper orders are rising each month as production begins to ramp up.

Chrysler also announces all of its engine and transmission plants will remain open throughout the summer except one of its Kokomo, IN, facilities.

Plants that will shut down will be closed for improvements enhancing future production, Chrysler says.

One-week closures affect Chrysler’s Toledo (OH) Supplier Park and plants in Belvidere, IL; Toluca, Mexico; and Saltillo, Mexico. Shutting down for two weeks are factories in Sterling Heights, MI; Warren, MI; Windsor, ON, Canada; and Brampton, ON, Canada.