Abstract: An auxiliary supporting frame for receiving drive shafts of a vehicle, wherein the auxiliary supporting frame has longitudinal supporting arms and transverse supporting arms connecting the latter to each other in order to form a closed frame shape, and wherein one or more openings are provided for the passage of drive shafts or shaft sections, and having at least one stiffening sleeve element is arranged in the at least one opening in at least one longitudinal supporting arm or in a section of the auxiliary supporting frame, and the sleeve element is fitted in such a manner into the opening between shells, parts or walls of the at least one longitudinal supporting arm, which is designed as a hollow body, the said shells, parts or walls forming a longitudinal supporting arm, and is fastened in such a manner to the shells, parts or walls of the at least one longitudinal supporting arm that it closes off the opening to the interior of the hollow body in a sealing manner in order to form protection against corros