Drain plug: 8mm Allen Key
Fluid: 1.7 Litres of Castrol Transmax Manual FE 75W
Remove the intake pipe (flat head or 7mm socket on the jubilee clips) and air filter (T25 torx) to get clear access to the vent / filler.
The drain plug is located at the rear of the transmission on the bottom:
Drain and fill with 1.7 litres of Transmax Manual FE 75W.
Re-fill via. the breather (just pull the cap off). There is what looks like a filler plug (10mm allen key) at the top of the transmission but this is not a filler.
Job done!
Don’t fill the gear box through the expansion breather port. There’s a fill point on the side of the gear box. You just pump the oil in until it starts flowing back out of the hole and then you know it’s at the correct level.