A work vehicle monitoring system includes a work vehicle and a monitoring device provided on an exterior of the work vehicle. The work vehicle includes a steering clutch, a rotary member having a first hydraulic fluid supply channel, a drive unit, a support member having a second hydraulic fluid supply channel, a sealing ring disposed between the first hydraulic fluid supply channel and the second hydraulic fluid supply channel, a controller that controls a pressure of a hydraulic fluid inside the first hydraulic fluid supply channel and the second hydraulic fluid supply channel, and an external output component that outputs data related to the pressure, a rotational speed, and a time. The monitoring device accepts the data from the external output component and outputs maintenance information about the sealing ring when a predicted wear amount of the sealing ring obtained from the determination basis data exceeds a specific threshold.