Lewis Hamilton's nightmare Japanese Grand Prix weekend hit another trough when it was confirmed he would receive a five-place grid penalty in tomorrow's race.

The McLaren driver suffered an oil pressure problem which forced his team to change his gearbox, triggering the penalty.

"In third practice we noticed abnormal gearbox oil pressure on Lewis' car, which we believed we had corrected ahead of the qualifying session," said a McLaren spokesman. "As we fired up Lewis' car several times in preparation for qualifying, we became aware that the symptoms were worse than we'd originally diagnosed, and a decision was later taken to change the gearbox."

In the event, there was no qualifying hour on Saturday as torrential rain forced its postponement until Sunday morning, robbing Hamilton of yet more track time after losing over two hours of set-up work on Friday after a shunt in opening practice.

The 2008 world champion's troubled weekend comes as he is bidding to get his championship challenge back on track after failing to finish three of the last four grands prix.

He trails championship leader Mark Webber by 20 points ahead of Sunday's race.