North American auto makers built 1,423,256 light vehicles in April, including 638,777 cars and 784,479 trucks, up 13.7% from year-ago.

The gain partly was due to more production days than in 2012, as Easter fell in March this year instead of April.

Ford-Mazda’s Flat Rock Assembly joint-venture plant saw a decline from year-ago, having dropped production of the Mazda6 sedan. However, Ford Mustang output rose 6.7% in April. Output will be boosted by the addition of the new Ford Fusion in late August.

Detroit Three production grew 11% in April, compared with like-2012. Ford enjoyed the biggest gain, up 19.7%, with 263,553 cars and light trucks. Chrysler rose 12.7% to 215,858 units and General Motors, which barely held onto its top manufacturer ranking last month, was up 2.5% to 270,096.

Unlike Ford and Chrysler, GM built fewer vehicles in April than March, most likely to control inventory. Additionally, its Saltillo, Mexico, plant phased out production of the current-generation Chevrolet Silverado and GMC Sierra pickups in order to ramp up for new versions of the trucks this month.

Among the transplants, Toyota and Honda recorded their first monthly double-digit gains for the year. Toyota built 164,993 vehicles in April, up 13.8%, marking the first month since September 2012 that it surpassed Honda, up 17.3% to 160,764.

North American production through the first four months rose 4.1% to 5,417,728 units from like-2012.

U.S. output climbed 16.4% to 976,508 units in April from year-ago, with the 4-month total rising 6.5% to 3,669,523. Mexico improved 15.9% to 237,587 in the month and rose 5.4% to 963,419 through April. Canada inched up 0.5% to 209,161 in the month, but fell 6.8% to 784,786 year-to-date.

eberger@wardsauto.com