Lot of talk of pod nod. Agree that its caused by VIGV's or fuel flow reg and should be reported but not sure I would call pod nod vibration! Rolls say pod nod has a frquency of 1-4 Hz and having had it a lot in the passed I wouldn't call it vib. I've had engine vibe that didn't show on the guages our boffins said it was too low a frequency but don't discount an airfame reason, gear door, cargodoor(aircraft doesn't have much diff on) or a wheel thats got a good flat spot vibrates like hell as its spinning down( you can feel the nosewheel realy well on the flightdeck or front gally).
Top marks for brining to the flightdecks attention. Free beer for you I think.
Kenny your buying but don't leave before she brings the tab.