MONTREAL, Canada - Gearbox troubles left Jenson Button kicking his heels for much of Canadian Grand Prix practice while McLaren team mate Lewis Hamilton was fastest in both sessions.The contrast between the two Formula 1 champions was extreme but Button and the team remained optimistic after a difficult day for one side of the garage at the Circuit Gilles Villeneuve.Button won a rain-hit race in Canada in 2011 after a collision with Hamilton, who took his first win at the circuit in his 2007 debut season, left him having to fight from the back of the grid after a re-start.'IT'S NOT A DISASTER'Briton completed 12 laps in the first session and 14 in the second with mechanics having to carry out lengthy transmission changes.He made it out on track with just 18 minutes remaining in the second session and then hit traffic, but despite that was ninth fastest.Team principal Martin Whitmarsh said: "It's not a disaster. Obviously he knows the circuit, he's a pretty experienced driver, he was pretty good here last year and I think we can recover the situation tomorrow and I'm sure we will. "It's nice to get the miles in, but Lewis was doing some good long runs and some good short runs so we've got quite a lot of data anyway within the team and that feeds across to Jenson," he said.TRANSMISSION WOESMcLaren managing director Jonathan Neale fended off accusations that McLaren had taken far too long to fix the problem.He explained that oil was leaking onto the clutch of Button's car. Once the seal had been repaired and the gearbox rebuilt, the mechanics discovered another previously undetected problem when the engine was fired up.This forced a second gearbox change.Button said: "I'm not too worried. The car has been quick all day, so there's lots of good information for us to look at for tomorrow. I enjoy driving around this place so we'll be hoping for a bit more luck tomorrow.”In six races, he has failed to score three times.Stay with Wheels24 for the Canadian Grand Prix weekend!