A method for shifting a PTO transmission includes selecting a PTO output speed from one of a first PTO speed and a second PTO speed of the PTO transmission, operating the PTO transmission in a reduced power mode at the selected PTO speed, the reduced power mode providing lower power to the PTO transmission at the selected PTO speed than a normal operating mode, comparing an instantaneous drive power to a maximum drive power in the reduced power mode, and when the instantaneous drive power exceeds the maximum drive power, automatically shifting the PTO transmission under load from the reduced power mode to the normal operating mode and automatically adjusting a transmission ratio of a vehicle transmission.