In the other game, Armour Wood '81/85 kicked off its semifinal bid with a 71-57 thrashing of Asian Home Appliance '89/93.
Four players scored in double figures led by Danel Hayag with 21 points as Class 2004 assured itself of at least a tie for the Division II finals berth with a 2-1 win-loss record.
Hayag was heavily backed up by Rodney Co with 17 points, and Christian Espada and Aljhune Areja, who finished with 16 and 15 markers, respectively.
After a 69-all deadlock at the end of the regulation period, Class 2004 banked on its fresher legs and quickness to finish off Class '95 with a 15-8 run in the extension.
Donald Anthony Ting fired a game-high 27 points, 17 in a 23-15 first quarter rally, but his efforts went for naught at Class '95 started its semifinal campaign on a wrong foot.
Earlier, Class '81/85 showed great team effort in pulling of a 14-point rout of Class '89/93, behind 23 points from cat-quick playmaker Stephen Lee.
Joel Chan added 19 points, while Wilson Yu and Edwin Kaw connived for 26 points for Class '81/85, which ripped the game apart with a 54-40 edge entering the final quarter. The Armour Wood-backed squad never looked back from thereon.
Allan Leith Ting finished with 18 points but was the only double digit scorer as Class '89/93 absorbed its first semis defeat in two starts.
The scores
First game
Class '81/85 (71) - Lee 23, Chan 19, W. Yu 14, Kaw 12, J. Yu 2, Aberia 1
Class '89/93 (57) - A. Ting 18, Mendez 8, Ng 8, Tan 6, Chua 6, Chiang 4, Ong 4, Lauron 2, E. Ting 1
Second game
Class 2004 (84) - Hayag 21, Co 17, Espada 16, Areja 15, Uy 6, Sypongco 6, Mamac 3
Class 1995 (77) - D. Ting 27, Yu 11, Gue 10, Ho 7, Ong 7, Tiu 5, Angcay 4, Gollon 4, Co 2