A driven steering shaft assembly especially for a planetary steering shaft is formed with a universal joint interposed between an axle shaft extending from a differential and a steering shaft for driving a wheel hub or the inner central gear of a planetary set, with the universal joint coupling the axle shaft and the steering shaft together. The universal joint includes an outer joint member coupled with one of the shafts and an inner joint member coupled with the other shaft. A sealing boot is operatively coupled to seal the interior of the universal joint and the sealing boot is releasably attached with the outer joint member of the universal joint. A neck portion of the sealing boot engages the steering shaft in releasable connection therewith but axially slideably movable relative thereto. The sealing boot is formed with an inherent resiliency in the axial direction of the assembly enabling it to adjust to the greatest axial length and permitting the universal joint together with the axial sealing boot to be removed without detachment of the fastening means of the sealing boot.