The DJR Team Penske driver headed into the race as the favourite after taking pole position in qualifying, which arrived following a commanding to drive to victory in Race 9 on Saturday.
However, the Kiwi lost ground early in the race to Jamie Whincup before slipping to fifth position in the opening laps.
The New Zealander revealed after the race that his car had lost the electronic shift-cut, which allows drivers to upshift without lifting off the throttle.
“It happened when I came up behind Whincup and that's when I sort of lost my pace,” said McLaughlin.
“I was clutching (on the upshifts) and everything. It was old school. It was a battle.
“It made me really appreciate how much easier it is when you do have a gear cut and are able to just flat-change.
“I was trying a lot of different things to make it work and when the Safety Car came out I knew I'd be under fire.
“We just had to do our best and fifth was it.”
Although hampered by the issue, McLaughlin admitted that he didn't have the pace to challenge for the victory today.
During the race, he elected not to fight with a charging van Gisbergen and instead allowed his countryman and rival through relatively unchallenged.
“I don't think we had the pace today,” he added.
“I think we would have been a little bit better but Fabs definitely had a very fast race car compared to me.
“We could have been there or thereabouts but it would have been tough to win the race from our position.
“There was no point fighting Shane because he was coming through hard.
“I was catching Whincup when Shane was catching me, so I thought if I could let Shane go and he can chase Whincup and put pressure on him I might be able to catch up to him.
“Sometimes you've just got to pick your battles and that was one I just decided to let go.
“I could have held him up but I felt I needed to salvage what I had and if that was an easy third or fourth, which it would have been before the Safety Car, then that was good.”
McLaughlin is lying third in the standings 28 points adrift of team-mate Fabian Coulthard, who leads the championship.