Gear box leavel

[johndow]

hi all new to this ,well been thinking that the gear box could do woth some topping up or a new refill can some one say where the bleed nut is and where i would locate the refill valve and i know the check levle nut is on the side of the box but i have found out that there is a nut missing off the side of the gear box towards the bottom was thinking this was it but why would it be missing car in question is a pug 1.6 s hdi 90bhp on a 57 plate any answerts on this will be most greatfull