The Citroen Junior team will replace the gearbox on Kimi Raikkonen's Citroen C4 WRC after the Finn reported handling problems with the car on the opening loop of Rally Japan stages.
Raikkonen is lying 10th after dropping time on the morning's opening test when the car was stalling in tight corners, but it was the transmission problem which was more of a concern for the ex-Formula 1 driver.
"This was always going to be difficult rally," said Raikkonen. "It's a question of taking it easy for the first few stages. The car kept pulling to the right, which wasn't helping my confidence very much. But, OK, the main thing is that there have been no mistakes."
Citroen Junior team principal Benoit Nogier said the team would be investigating the problem on Raikkonen's C4.
"We don't know exactly what the problem is," said Nogier. "We will look at the data when the car is in service, but as a precaution we will be changing the gearbox."
Raikkonen suffered a similar handling issue on the final day of Rally Portugal earlier this season.