The only French driver in what amounts to a home race suffered gearbox damage on his way to eighth place in Spain two weeks ago and the governing FIA confirmed on Saturday that he would start with a new one in Monaco.
The rules say gearboxes must last for six consecutive events and Sunday's race is the sixth round of the season, meaning Grosjean must take a penalty.
Grid penalties in Monaco carry a much heavier weight than normal, given that it is extremely difficult to overtake on the tight and twisty street circuit. The race has been won by the driver on pole for the last six years.
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(Reporting by Alan Baldwin, editing by Amlan Chakraborty)
