I'd like to add Molyslip to the gearbox of my 2008 1.8 petrol Focus. But where is the filler plug and how do I get to it? Do I have to jack it up and remove the under-engine shield or is there a simpler way?

why do you want to add an additive to the gearbox? are you experiencing problems? have you changed the gearbox oil?

dont do it. only use the correct gear oil, pref fords own as that has its own friction modifiers in the oil. molyslip may cause more problems than it fixes.

If you have the 1.8 Duratec petrol engine it has the 5-speed IB5 gearbox. The IB5 gearbox has a combined filler/oil level plug. This plug is located behind the black cover at the front of the gearbox (near the shift mechanism). The filler/oil level plug can be removed with an Allen key. As an alternative the breather pipe on top of the gearbox can also be used to add a bit of oil/additive. The breather pipe is located on top of the gearbox below the air filter box. When adding oild/additive through the breather pipe you have to remove the filler.oil level plug to prevent the gearbox from overfilling.

On the IB5 gearbox the oil level must be between 5 mm below the filler/oil level plug and flush with the filler/oil level plug. Depending on the current oil level and the quantity of the additive you want to add it may be necessary to drain a bit of oil from the gearbox. The IB5 gearbox does not have a drain plug so using a vacuum pump to drain a bit of oil will be the easiest option.

My experience is that Ford only fills the bare minimum amount of oil at the factory. This way they save a bit of oil on every produced car which saves them a lot of money on the long term. My experience is that even on new cars the gearbox oil level is below the minimum level. In my opinion you should at least check the oil level.

Designed to be below level plug on a lot of ford boxes, not just from factory, usually 5mn below

On most new Ford gearboxes I have seen the oil level was much lower than prescribed. The first thing I do after I bought a car is checking all fluid levels including the gearbox oil level.

On my current Focus MK3 with the 6-speed B6 gearbox I had to add 0.4 Liter of oil before it reached the prescribed oil level.