The ship conducted three more WestPac deployments through 1965 before she returned to a schedule of local operations. "Tiru" entered another major overhaul on 6 December 1965—one which saw the installation of a masking system to cover the ship's own noise while snorkeling. Further internal alterations improved both her fighting capacity and her habitability. She conducted sea trials until 14 June 1966 when she departed Hawaii for the Naval Torpedo Station at Keyport, Washington, for an alignment and testing of her weapon system. The submarine departed the West Coast on 9 July, bound for Hawaiian waters, and made port at Pearl Harbor nine days later to commence pre-deployment operations.