General Motors is still building examples of the old Chevrolet Silverado and GMC Sierra as it’s ramping up production of the new one. And according to the latest, it’ll keep making them well into the new year ahead.

Automotive News reports that production of crew-cab versions of the previous-generation K2 model will begin winding down early in 2019, and output of regular- and double-cab models will carry on through next summer.

Managing production of two generations of pickups has been a delicate balancing act for America’s largest automaker, whose plant in Fort Wayne, Indiana, serves as its main hub for full-size pickup production. It also utilizes additional capacity at its plant in Flint, Michigan, and is preparing to begin production in Siloa, Mexico, to help keep up with demand for the new T1-generation Silverado and Sierra.

But to handle assembly of the “legacy” K2 models, it’s been shipping unfinished trucks across the northern border to Ontario for final assembly in a process known as the “Oshawa shuttle.” The program has been such a success that GM plans to build even more trucks than originally expected – about 60,000 per year – in Oshawa.

GM isn’t the only one that’s still building its old trucks as it rolls out newer ones. FCA is doing the same with its Ram 1500, positioning the legacy version at fleet buyers and the new one at private consumers. Both GM and FCA are eager to take a bigger slice of the lucrative full-size pickup market that’s dominated by the Ford F-150.