6 speed box

[cancunia]

when I looked at the bottom of my gearbox there are 2 apparent drain plugs, one is as you say a square key plug whilst the other is just a normal plug, maybe 22mm, thought that the square one was for final drive maybe.

It's possible we don't have the same gearbox, but I remember having to grind down a big Allen key to a square so I'm fairly sure that's what mine used as a drain. Maybe I undid the wrong one, but a lot of oil came out!