Seabrook picked up a loose puck and skated in on Howard through the middle of the ice, with Detroit defenseman Niklas Kronwall in front of him. His shot hit Kronwall's leg before it sailed into the left side of the net for the defenseman's first goal of the postseason.
"I don't know if I saw it go in to be honest," Seabrook said. "I just heard the horn going and the boys jumping out. It was a pretty exhausting game, but I think I was more tired during the celebration with guys jumping and pushing me in the face and dragging me down.
"It's exciting. You don't get to do that too many times."
The sellout crowd of 22,103 roared as Seabrook skated over to the boards and was mobbed by his delirious teammates.
Howard put his arm around Kronwall, who was down on one knee, and tried to console him while the Blackhawks celebrated.
It was quite a change from the end of the third period, when the Blackhawks thought they had scored the go-ahead goal. But it was waved off with less than 2 minutes remaining by referee Stephen Walkom, who called a pair of penalties behind the play.
Patrick Sharp had given Chicago a 1-0 lead in the second period.
Henrik Zetterberg tied it in the third for No. 7 Detroit, which beat second-seeded Anaheim in seven games in the first round. Howard finished with 33 saves.
Red Wings forward Pavel Datsyuk was held without a point, closing out an ineffective series for the Russian star.
O Conference finals
• Boston at Pittsburgh, 6 p.m.
• Los Angeles at Chicago, 3 p.m.