Depends if you have the standard gearknob, which you should be able to pull off after you've got the gaiter off. If you have the metal SP gearknob though, time to get the hacksaw out. Getting the knob itself off is a question of undoing a screw, but then there's a plastic bit glued on underneath, like a 5 inch long plastic sleeve which you'll need to cut away. Only thing you can do is persevere with it, it's a nightmare.