Abstract: A planetary gear transmission unit includes a planet carrier which supports and locates circumferentially spaced pairs of planet gears, and at least one planet shaft. The planetary gear transmission unit further includes a planet shaft locking mechanism between the at least one planet shaft and the planet carrier for preventing the at least one planet shaft from rotating around its own axis, the planet shaft locking mechanism being provided between an axial end face of the planet shaft and the planet carrier in a direction substantially parallel to the planet shaft. An advantage of the planetary gear transmission unit is that rotation of the planet shaft relative to its axis in the planet carrier is prevented. The unit results in a free of wear contact between planet shaft and planet carrier, thereby allowing all degrees of freedom of the planet shaft without disturbing the load distribution between the planet gears of a pair on one planet shaft.