Jamie Whincup says his car “wasn’t making any sense” on Saturday at the BetEasy Darwin Triple Crown until Triple Eight Race Engineering discovered a crack in the chassis.

Whincup earned eighth on the grid in Armor All Qualifying for Race 15 and used a combination of strategy and car speed to claim fifth position in the 42-lap encounter later that afternoon.

However, he and team-mate Shane van Gisbergen both missed today’s Armor All Top 10 Shootout, after which Whincup suggested that they had not been able to get their heads around ‘dramatic’ set-up changes.

Those changes were made after the Red Bull Holden Racing Team discovered a “problem with the car” overnight, although the exact nature of that problem had not been disclosed until after Race 16.

“At the risk of looking like I’m diving into the excuse book, part of the chassis was cracked and the car wasn’t making any sense all weekend,” Whincup told Speedcafe.com.

“That really hurt us, to try and fine-tune and be competitive.

“It was flexing and it was throwing the corner weights out, it was doing all sorts of things, so the car wasn’t making sense and we just thought it was a matter of tyres going off and whatnot.

“We were lucky to find that last night. It did completely change the car for this morning and we didn’t quite nail it this morning for quali but got it right for the race.”

Starting from 11th, Whincup was twice bumped off the road on the first lap of Race 16 and fell to second-last in the 25-car field, before driving back to fifth at the chequered flag.

“That was the story about the quali pace but (in) the race, the car was good and we were able to get ourselves out of trouble, some good strategy work and a quick car allowed us to come from 24th to fifth,” he added.

While the chassis was fixed in time for Sunday morning qualifying, Whincup suggested that there may be further work when it returns to Triple Eight’s Banyo workshop.

“It was literally the mounting that comes down that holds the rocker for the rear rollbar, so it’s the same for every car, so we just welded it up last night,” he explained.

“We might have a bit more of a look at it when we get back but it was pretty good today.”

Whincup sits sixth in the championship after the trip to the Top End, nine points and one position behind van Gisbergen.