There are a couple Service Bulletins (SB) that L-3 Communications have issued for their vertical gyros that I highly recommend. They will reduce vibration issues and result in better drift characteristics, making the gyros more stable.
SB501-1204-19 (Rev. D), Modification 22 was issued in May 2005 to improve gyro performance by replacing the double row bearing on pitch axis with a single row bearing.
SB501-1210-15A, Modification 16 was issued in May 2001 to improve drift and vibration performance and eliminate potential of spring on pitch axis from rubbing on shield of bearing.
There are no costs to complying with these SBs, if they are accomplished during overhaul.
Gyros are an essential piece of business aircraft avionics equipment and you invest a lot of money to keep them airworthy. With proper gyro handling and storage methods, they can operate properly for many years. When it comes time to send in your gyro unit for overhaul, always follow the two-box method for shipping.
Collins Aerospace TDR-94D Transponders