That's the ball at the bottom of the gear stick Bob. It allows the stick to move through the different positions when you change gear. The ball is usually greased and has a strong spring if you have to push down or lift the stick up to change into reverse. You could check if the ball is greased and moving freely by removing the surrounding gaiter or the console depending on the car. It's not usual for that to cause problems though and it probably won't be anything to do with the gearbox itself.
Is the gearstick hard to move? Depending on the car it sounds more like the selector levers could be getting sticky. They are rods connecting the bottom of the gear stick to the gear selectors on the gear box. They can become dirty, bent or rusty - whatever. If you feel confident, remove the rubber/cloth gaiter surrounding the gearstick then check the selector mechanism for free play and make sure everything is well greased. Otherwise ask a garage to have a look for you.
Good luck.



