Transmission noise (?)

[Dihydrogenoxide]

Yup, done by the previous owner. The strangest thing was that the Honda mechanic told me he reckons it's a leaky o-ring, but my mechanic (who is a hell of a lot closer than the nearest honda dealer) couldn't find a single o-ring that wasn't perfectly adherent to its job description.

[Jiblet]

I have the same deal. Very noisy when in 3rd gear and dropping revs.
I am leaning towards a clutch related problem and as stated earlier, could be thrust bearing (which is no big deal as brand new ones can make noise).

Have a look at where your motor mates to your gearbox/diff area. I found that there was a chip out of the casing and that I could actually see the flywheel.