Abstract: Power actuator unit for servo-drive of motor vehicle body closures e.g. centrally controlled door latches and locks, window winders etc and including a power transmitting drive train wherein the latter includes a female bearing surface, e.g. the bore (34) of a boss (30) of a gear wheel or pinion (31) which is a running fit on a complementary male bearing surface e.g. a metal shaft (32). One surface e.g. of the shaft is at constant radius from the axis of relative revolution of the surfaces e.g. is cylindrical; and the other surfaces e.g. the bore (34) is formed to have a plurality of facets or other sections e.g. by being square in diametral cross section to provide line or point contact with the one surface at sufficient angularly spaced locations to ensure true running but the facets or sections not being otherwise in contact with the one surface e.g.