TORONTO (Reuters) - Workers at Toyota Motor Corp's (>> Toyota Motor Corp) Canadian plants are set to vote next week on whether to become the first at wholly owned Toyota facilities in North America to unionize, a push Canada's biggest private-sector union is confident will succeed.

A "yes" vote would mark a major victory for the union, Unifor, which has more than 300,000 members, including more than 39,000 in the auto industry, even though previous attempts to organize Toyota's Canadian plants failed.

"There's no question, there will be a lot of eyes on this drive," Unifor President Jerry Dias said at a press conference on Monday, where he was flanked by Toyota employees who said they wanted a bigger say in their workplace.

Unifor, which filed for union certification at Toyota with the Ontario labor board on Monday, said it did not want to say exactly how many workers have signed union cards, citing strategy. It said, however, that of the 6,500 workers at the three Toyota assembly plants in Ontario, well over the 40 percent needed for a vote to be held have signed cards.

The results of the vote, which is expected to start on Monday, will not be known until later in April, the union said. More than 50 percent of workers would have to vote "yes" for a union to be formed.

Toyota Motor Co of Canada, which has two plants in Cambridge, Ontario, and one plant in Woodstock, Ontario, said that its workers already "have a package that's at, or near, the top of the industry" and that it was uncertain what more a union could offer.

"We don't know what they're going to be able to negotiate or, frankly, what they're going negotiate away," said spokesman Greig Mordue. "What Unifor can offer is, frankly, a mystery."

He added that Toyota Canada, which began assembling vehicles in Ontario in 1988, has never laid off a permanent employee.

Mordue said that that record stands despite such challenges as the recession, and a 50 percent drop in production for two months earlier this year due to supply chain disruptions.

If a union is formed, collective bargaining would begin immediately, Dias said, and would address such key issues as wages, pensions, contract work, and health and safety standards.

Negotiations would create a Toyota-specific contract, he added, and not be a "carbon copy" of what was negotiated with the Detroit 3 in Canada in 2012. Unifor represents workers at the Canadian arms of General Motors Co (>> General Motors Company), Ford Motor Co (>> Ford Motor Company) and Fiat Chrysler Automobiles (>> Fiat SpA).

"The auto industry in Canada, and Ontario specifically, is a C$69 billion ($62.51 billion) a year industry and we want to protect it," Dias said. That means the union would not negotiate a contract at Toyota with labor costs that were out of line with other manufacturers, he added.

Toyota workers are unhappy with temporary contracts, Unifor has said, which have reduced benefits and don't allow participation in the company's pension plan. About one-quarter of Toyota's 6,500 workers are contract workers, Dias said.

The pension plan is also an issue after the company said last year that it would put new permanent hires on a defined contribution plan, versus a more costly defined benefit plan.

HOME-GROWN ROOTS

Unifor said part of its confidence in the Toyota campaign is a reflection of the movement's home-grown roots. The first union cards from Toyota in 2012 were photocopies that workers had made on the back of company bulletins, Unifor said.

The drive gathered speed with last September's high-publicity formation of Unifor, a merger of the Canadian Auto Workers union and the Communications, Energy and Paperworkers union, Unifor said.

At its two plants in Cambridge, the company manufactures the Toyota Corolla, Toyota Matrix and Lexus RSX 350. The Toyota Rav4 is made at a newer plant in Woodstock.

Toyota, which says its staffing is significantly higher than the 6,500 estimated by Unifor, can assemble more than 500,000 vehicles annually at its Canadian plants.

In 2008, the International Association of Machinists withdrew a bid to try to unionize the Canadian Toyota plants due to inadequate support. That followed a similar withdrawal by the Canadian Auto Workers in 2001.

Unifor's push comes after the high-profile failure of the United Auto Workers to unionize workers at a Chattanooga, Tennessee, Volkswagen plant.

Currently, the UAW represents just one foreign-owned U.S. factory, a Mitsubishi plant in Normal, Illinois, with around 1,000 workers. Overall UAW membership increased in 2013, however.

Unifor said that 90 percent of Toyota plants worldwide are unionized. Toyota previously had a joint-venture auto manufacturing plant in California with GM that was unionized, but it shut in 2010. The plant is now owned by Tesla Motors Inc (>> Tesla Motors Inc).

($1=$1.10 Canadian)

(Editing by Jeffrey Benkoe, Jeffrey Hodgson and Peter Galloway)

By Susan Taylor and Solarina Ho