The move will hurt those truck's fuel economy performance because those models, equipped with the 5.3-litre EcoTec3 V8 engine with both six-speed and eight-speed automatic transmission, will have lower fuel economy by one mile per gallon.

GM spokeswoman Michelle Malcho said all trucks were still being built, something GM has repeatedly stressed it would try to protect as pickups are among GM's most profitable models.

She declined to say the volume of vehicles affected.

"By taking this measure, we are better able to meet the strong customer and dealer demand for our full-size trucks as the industry continues to rebound and strengthen," Malcho wrote in an email. The change runs through the 2021 model year, which typically ends in late summer or early autumn", she said.