Prior to the 2008 season, Wood Brothers Racing and JTG Racing split into two teams. Ambrose was scheduled to drive for both teams in Sprint Cup competition in 2008. He was going to run twelve races in the No. 21 car for the Wood Brothers and another four in the No. 47 car for JTG Racing. However, due to various issues he only ran 11 of the 16 planned races. He ran well in the Toyota-Save Mart 350 at Infineon, qualifying 7th out of 47 drivers and was running in the top three, but his No. 21 spun through the famous Turn 11 hairpin and blowing his transmission, finishing a disappointing 42nd in the 43-car field. He attempted to make his second career Sprint Cup start in the Lenox Industrial Tools 301 at New Hampshire, but failed to qualify, qualifying 45 out of 45. Again, 43 cars would start, and again, he attempted to qualify the 21 car. He also drove the full Nationwide Series schedule.