What was found
(CAN) ON TAXI IT WAS NOTICED THAT THE VERTICAL GYRO HAD FAILED AND WAS APPROPRIATELY FLAGGED. THE FLIGHT CREW RETURNED TO THE BLOCKS WHERE MAINTENANCE REPLACED THE GYRO AND GROUND FUNCTION CHECKED THE SYS SERVICEABLE. THE GYRO WAS SENT TO AN AVIONICS SHOP FOR INSPECTION AND TO DETERMINE WHY THE GYRO FAILED SO SOON AFTER O/H. THE REPORT STATED THAT THE WASHER WAS INSTALLED BACKWARDS GIVING THE BEARINGS AN INCORRECT PRE-LOAD. THE REPORT WENT ON TO MENTION THAT THIS IS QUITE A COMMON MISTAKE AMONG O/H SHOPS THAT HAVE INEXPERIENCED TECH.