Captain Owen Bailey scored the golden goal for United's second-string as they won the seven-a-side tournament for a second consecutive year in the Happy Valley but were required to come from two goals down in the final after Andrew Dallas' first-half brace for the Gers.
Bailey's header and Luke Charman's fierce strike levelled the tie before Elias Sørensen, who was awarded Player of the Tournament, sent Newcastle into the lead from the penalty spot until Rangers' Josh McPake sent the clash into extra-time with a late equaliser.
Bailey was forced to play in a goalkeeping role as the game went to four-versus-four but the 20-year-old's winner, a calm precise effort into the top right-hand corner, secured United's third title in Asia.
Earlier in the competition, Ben Dawson's side finished top of Group C after 1-0 victories over Yau Lee League Select and Kashima Antlers, with Kelland Watts and Sørensen scoring the respective winning goals before a goalless draw with Brighton and Hove Albion.
In the knockout stages, Newcastle progressed to the semi-final with a 2-0 triumph over Portuguese outfit Portimonense courtesy of goals by Tom Allan and Sørensen before Ben Dawson's side set up a final meeting with Rangers, who the Magpies defeated in last year's final, as Sørensen netted a brace in their 2-0 semi-final victory over Hong Kong's Kitchee.