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Hi AA,

I have recently started having trouble with 4th gear in my manual 2006 Mazda3 hatch. It used to be totally smooth, and about 40% of the time it will change into 4th from 3rd smoothly, but the other 60% of the time it feels resistant, and it making metallic sounds (I wouldn't call it grinding). I do not get this in any other gear, the only other gear that has difficulty is reverse but that is because of the synchros. My clutch pedal is to the floor when I change gear, and the clutch is not slipping (I tested that today), so I am confident that the problem is not in there.

I find this quite difficult to describe to you, as it does not do it all the time and it sounds as if it might be in the shift linkage rather than the gearbox; the sound seems to generate right under the shift boot. I recently put on a new gear knob, and to get it on it needed a little bit of man-handling. I wonder whether I may have damaged a linchpin, or maybe the linkage itself?

Considering it is not doing it 100% the time do I need to get this looked at?

Many thanks,
Dave

Hi there,
If the sound is under the gear linkage boot area, it could be a coin or pen that has fallen down the side (more common than you might think).
Or if it's inside the gearbox, the first thing checked might be to replace the fluid and check for contamination. It could be that particular syncro is worn-out and might only get worse if not checked.