Defender 90 gearbox drain plug

[b19nor]

Hi guys I seam to be missing a drain plug next to gearbox of my 300tdi Defender.
Anyone tell me what one it is

[anonymous-user]

That's bell housing drain hole, to allow any excess crud or gearbox oil seepage from collecting around and possibly contaminating the clutch.
It's threaded so you can, if doing a lot of wading, insert a wading plug which prevents water and crud getting in to the bell housing in the first place.
Under normal operation and occasional water crossing it should be left open.
You haven't been running a dry gearbox

[b19nor]

Cool