According to the Haynes manual, it says that on my year of Astra (1996), there is no need to top up the gearbox. F18 CR.
Im intermittently having problems engaging all gears, although generally they slide in without too much force.
I know this problem might be related to something else, but see no harm in making sure the gearbox is topped up before investigating further.
Any ideas where the damn fill hole is, with pic if possible.
How would i know when there is enough in it ?
What a coincidence, I only just changed my gearbox oil today.
Changing the oil can't hurt and is advisable if it's done a lot of miles. There should be a bolt to under on the side of the gearbox to check the level. It should just about allow a trickle of oil to flow if it's topped up enough.
On my car the filler plug is a 17mm bolt on top of the transmission with a plastic cap.