I've just completed a gearbox oil change on my 2.0T Signum (F40 gearbox). All has gone well, and did it with a method that takes half the time compared to the Haynes way. I've taken several pictures, so I'll make a How2 from it this w/e.
There are 3 reasons why I did it. Firstly because new oil has to be better for the gearbox than oil that's done 67k. Secondly it was a chance to add in Molyslip Gearbox Protector grease. Thirdly, crucial to my query here, F40's of the vintage of mine come with 3.2 litres of oil in them, whereas the later ones have 2.4 litres in them, which makes the gearchanges smoother. Reducing the level of oil by 0.8 litres to 2.4 is an official Vauxhall fix for F40 cars with crunchy gearchanges.
When I drained the old oil out, I suspected that (as with engine oil) not all of it would come out - some stays in there even though you give it plenty of time to drain. So, I measured how much had come out and it's 2.8 litres, which means I may have up to 0.4 litres still in there. Can I be sure though?
It's crucial to know how much oil is still left, because if you don't take that into account and put in the required 2.4 litres of new oil, you may end up with 2.8 litres in total - which is too much and may not give me the crunch-free gearchange I'm after.
So, I've put in 2 litres, which may now give me the correct amount - 2.4 litres in total. My question is, does it sound plausible that 0.4 litres stayed in there? Or is it more likely that none stayed in there and now I've only got 2.0 litres in there, which is too little? I haven't started the engine yet after the oil change and await your replies please.
Note: On the F40 there is NO oil level dipstick and you don't fill it until the oil comes out of a hole in the side - you only know the oil level by knowing how much went in.