[3] The issues with the Collins class highlighted in the McIntosh-Prescott Report and the pressing need to have combat-ready submarines in the RAN fleet with the pending decommissioning of Otama, the final Oberon-class submarine in Australian service, prompted the establishment of an A$1 billion program to bring Sheean and sister boat Dechaineux up to an operational standard as quickly as possible, referred to as the "fast track" or "get well" program.

[11] The fast track program required the installation of reliable diesel engines, fixing hydrodynamic noise issues by modifying the hull design and propeller, and providing a functional combat system.

Teddy, realizing that the men in the water would be massacred by the incoming Japanese zeroes, manned an anti-aircraft gun, successfully downing 3 aircraft.

[18][19] During two weeks of combat trials in August 2002, Sheean demonstrated that the class was comparable in the underwater warfare role to the Los Angeles-class nuclear-powered attack submarine USS Olympia.

[21] Sheean was docked for a long maintenance period in 2008, but workforce shortages and malfunctions on other submarines requiring urgent attention have drawn this out: RAN and ASC officials predicted in 2010 that she would not be back in service until 2012.

[25] On 21 September 2021 Sheean experienced an emergency during a training exercise when water entered via a pump and the automatic system that is intended to respond to such malfunctions failed.

The Navy stated that the submarine had experienced a "minor flooding incident" and had not been in danger of sinking, and that it returned to service within a few days of the accident.