These grease cartridges need to be changed every year. There is one cartridge per unit, one on the parallel and one for each right angle unit. There is a window on the cartridge for recording the date of the replacement. It is very difficult to tell when they are empty, since they release grease so slowly, but they are designed to last only one year.
To install, remove operator-side covers, unscrew old cartridge, and wipe off excess grease from gears and from inside the cover.
Then screw on the supplied activator screw onto the back of the cartridge. It has a ring on the end that you put a screwdriver into and tighten into the cartridge until it breaks off. This activates the slow release of the grease. Dont worry, you wont see grease coming out immediately.
Then screw the cartridge into the grease tube. Some models you screw the grease tube onto the cartridge, and then mount the cartridge in a ring, and other models have a tube mounted that you screw the cartridge into. Either type may need some aiming of the tube into the gears, making sure to not touch the gears.
Record the date on the cartridge.