After losing his NASCAR ride, Leffler had been racing dirt car events most of this year, including the 410 Sprint Car race on Wednesday that promised a $7,000 prize to the winner at the 0.625-mile (1-kilometer), high-banked dirt oval. On Sunday, Leffler finished last at Pocono in his lone NASCAR Sprint Cup start of the year.
From Long Beach, California, Leffler made 423 starts in NASCAR's three national series, but won just the two Nationwide races and one Truck Series event in a career that began in 1999. He also made three IndyCar Series starts, finishing 17th in the 2000 Indianapolis 500.
Leffler's last full NASCAR season was 2011, when he ran the entire Nationwide schedule for Turner Motorsports. He finished sixth in the standings that season and hadn't had a steady NASCAR ride since.
Leffler is survived by son Charlie Dean.