McLaren is confident that there will be no repeat of the gearbox problems that hit both its drivers at the Singapore Grand Prix.
Lewis Hamilton retired from the lead at the Marina Bay circuit when his gearbox failed while Jenson Button was fortunate to finish after suffering a similar problem - but will get a grid penalty in Japan because he needs a new unit fitted.
McLaren technical director Paddy Lowe said that the issues had been traced back to a quality control issue - which had been resolved by the team since the Singapore weekend.
"It was the same [problem] on both cars actually, just more extreme in Lewis's car so it was then terminal," explained Lowe.
"Jenson was, to be honest, quite lucky to finish, and the gearbox was not in a good state at the end. So that is why we had to change it.
"It was a quality problem that unfortunately affected both of those gearboxes, but we completely understand it now and it won't crop up again. It had affected a certain batch."
Lowe added that there was no obvious explanation for why several teams had been dogged by gearbox failures this year, even though the five-race requirement is now well-established.
"In relation to our problems we have had, there is no linkage to the regulations this year or tyres this year," he said. "These are things that we have to learn how to handle year in and year out actually.
"It is very difficult, as you can appreciate, to build a new gearbox each year in a very limited amount of time, and type approve it to run five races uninterrupted.
"In our case, committing to it across two teams [McLaren also supplies Force India] is a big pressure on the system.
"It is tough, and what is making it [particularly] tough these days is the programme demand and timing of that in relation to the high endurance that is needed. It is quite an unforgiving set of rules in relation to penalties."