DOVER, Del. -- Jimmie Johnson's 500th career Cup start did not end the way the driver would've hoped.
Just past the 100-lap mark Sunday at Dover International Speedway, Johnson had to take the No. 48 Lowe's Chevrolet SS to pit road, and ultimately the garage.
Johnson said he didn't know exactly what happened, but a rear axle seal was the culprit.
"Something very inexpensive and simple, but that's racing," Johnson said of the issue. "I've lost championships this way, I've won championships this way with others having this issue."
The problem meant Johnson was 37 laps down when he returned to the racetrack, and he was able to gain two positions in the remainder of the race to finish 41st.
In the process, he was eliminated from the Chase for the NASCAR Sprint Cup.
"It's not the way we want to end the season -- it's unfortunate it's turned out this way, but it's racing," Johnson said. "There's not much we can do about it."
Johnson, asked to reflect on the way his 2015 quest for a seventh championship came to an end, said it shows just how important all 10 races are in the Chase -- even in the new round-by-round format.
"It wasn't meant to be," he said. "It's unfortunate. I feel for my team, I feel for Hendrick Motorsports, Lowe's, Chevrolet, but not much we can do about it. It's just racing."