At the start of 1969, the RAN's ship designation and numbering system was altered from the British pennant system to a new system based on the United States' hull classifications: "Sydney" was assigned the pennant number P214. The troopship began her thirteenth voyage on 8 February 1969, when she sailed from Fremantle with 5 RAR aboard. "Sydney" and the destroyer escort "Derwent" arrived in Vũng Tàu on 15 February and departed the same day with 1 RAR embarked, with the troopship reaching Townsville on 25 February. A training cruise in March saw the ship visit New Zealand and Fiji. "Sydney"'s fourteenth voyage, to deliver 6 RAR to Vietnam and return with 4 RAR, commenced on 8 May when "Sydney" sailed from Townsville. She met the destroyer "Vampire" off Singapore on 14 May, reached Vũng Tàu five days later, and arrived back in Brisbane on 30 May. On 17 November, "Sydney" and the destroyer "Duchess" departed Brisbane on the troopship's fifteenth voyage to Vietnam, with 8 RAR aboard. The ships reached Vũng Tàu on 28 November; 8 RAR was replaced by 9 RAR, which was delivered to Fremantle on 5 December.