Most gearboxes have a fill port and a drain port. These two access ports can be used to install a few important accessories. For example, on the fill port, a breather, vacuum indicator and quick coupler can be added. On the drain port, a quick coupler and an oil sampling valve can be installed. Watch this video by clicking the image below to discover how these accessories can be used to remove dirt particles, indicate when a breather is plugged, introduce makeup fluid, periodically clean or flush the oil and obtain an oil sample.