Earnhardt, grandson of seven-time Cup champion Dale Earnhardt and nephew of Dale Earnhardt Jr., will drive in nine Xfinity races in the Joe Gibbs Racing No. 18 car in 2019. He will bring sponsorship from security and military technology integration company Xtreme Concepts.
"I've worked incredibly hard for this opportunity, and I've got to thank Xtreme Concepts for making it happen," said the 29-year-old Earnhardt. "You see the level of expertise Joe Gibbs Racing has and the caliber of equipment they bring to the race track every week.
"As a driver, it's exactly where you want to be. It's the best opportunity I've had in my career, and I plan to make the most of it."
Earnhardt has 75 career Cup starts, mostly for underfunded teams, with a career-best 11th at Daytona in July driving for Premium Motorsports. He has 66 Xfinity starts (none since 2015) with a career-best of 12th at Bristol in 2014 and at Talladega in 2015. He finished 18th in the 2014 Xfinity standings driving for JD Motorsports.
His nine-race schedule will include the season-opening race at Daytona. The rest of the schedule was not announced for Earnhardt, as the No. 18 car typically includes a mix of Cup drivers and young drivers -- and often young drivers with potential who also have sponsorship.
Preece used the part-time path to make it to the Cup Series. Preece drove four races for JGR in 2017 and won one with four top-5s. He has competed in 13 races for the team this year with one win and six top-5s, and it was announced in September that he would replace AJ Allmendinger in the JTG Daugherty Racing No. 47 Cup car next year.
"Our Xfinity Series program is the perfect example of what happens when preparation meets execution," said JGR chief operating officer Coy Gibbs. "We've had both up-and-coming and veteran drivers achieve success in our race cars, and that success has translated to the partners they've represented.
"We think Jeffrey Earnhardt has the talent to win races and deliver strong results for Xtreme Concepts."
Xtreme Concepts will use the sponsorship to promote its iK9, a provider of service and protection dogs.