(Adds details on shifts and vehicle production, Unifor study on economic impact, worker comments)
By Susan Taylor
TORONTO, Jan 9 (Reuters) - Workers at General Motors Co assembly plant in Oshawa, Ontario staged a sit down protest that interrupted production for about two hours on Wednesday morning, a union spokeswoman said, following a similar protest late on Tuesday.
The action came after Unifor, the union representing the autoworkers, failed to win GM's support for its proposals to save the plant. Unifor, which has vowed to block GM's plan to close Oshawa by the end of 2019, met with GM officials in Detroit on Tuesday.
While different parts of production were shut down Wednesday morning, the entire line was halted intermittently, said Unifor spokeswoman Kathleen O'Keefe.
The union was not able to quantify the impact on production, noting the line typically assembles 300 Chevrolet Impala and Cadillac XTS cars per shift.
On Tuesday night, truck assembly stopped completely for nearly five hours, Unifor said. The shift, which typically assembles 225 Chevrolet Silverado and GMC Sierra trucks, only completed 55 vehicles, the union added.
It was also unclear if any work stoppages would coincide with a Unifor rally in Windsor, Ontario on Friday.
"The majority of people are prepared to battle GM and try to get them to change their decision," said Tony Leah, a welder at Oshawa for over 38 years. "I wouldn't classify that as hopeful. I would classify that as angry and determined."
Oshawa's closure, which GM said would affect 2,973 assembly-line jobs, was announced in November as part of a broad restructuring aimed at cutting costs as investments increase in electric and autonomous vehicles.
GM has also not allocated new products for four U.S. plants, raising the possibility of closure and the elimination of a total of about 15,000 jobs in North America.
"We understand our union's frustration, but need to now work together to deliver supports, transition and training for our employees," said GM spokesman David Paterson.
In 2020, the closure is forecast to reduce Ontario's GDP by C$5 billion ($3.78 billion) and cost 4,000 jobs, according to a study by QED Inc consultancy, commissioned by Unifor and released on Wednesday. By 2025, 14,000 jobs are projected to be lost in Ontario and another 10,000 across Canada.
While Oshawa's production capacity is 310,000 vehicles, 2018 utilization was 22 percent, according to LMC Automotive. ($1 = 1.3220 Canadian dollars)
(Reporting by Susan Taylor; Editing by Bernadette Baum and Lisa Shumaker)