MEXICO CITY (AP) — A new independent union at a Mexican auto plant that won a historic organizing vote last year has negotiated an 8.5% wage increase for unionized employees.

Authorities said Friday that workers at the GM transmission and pickup plants in the northern Mexico city of Silao voted overwhelmingly to approve the new contract, which also increases benefits by 2.5%.

The federal labor board said that in voting Wednesday and Thursday, 87% of the plant’s 6,331 unionized employees voted in favor of the new contract.

Plant employees had not previously been able to vote openly, by secret ballot, on contracts or who would represent them. The Independent Union of Auto Industry Workers, known by its initials in Spanish as Sinttia, won an organizing vote in February after ousting an old guard union last year.

The Sinttia union said the contract actually increases benefits by 5.3%. Mexico’s inflation rate was running at nearly 7.7% in April, meaning the wage and benefit package combined was above inflation.

The new contract “represents a significant improvement over the labor conditions we had, and an improvement in wages and benefits,” the union said in a statement.

The events at the Silao plants are seen as a major test of whether a measure of freedom has come to Mexico, where pro-company unions held wages down for decades and drained manufacturing jobs from the U.S.

The union representation vote was held last year only after the U.S. government filed a labor complaint under the U.S.-Mexico-Canada free trade pact. Under changes to Mexican labor law required under the USMCA, workers can now in theory vote out the old, pro-company union bosses. But in practice, the old union bosses have resisted.

One such CTM union had been in power at the GM plant in Silao, and when workers voted on whether to oust it in April, Interior Department inspectors “discovered that at the offices where the union itself had the ballot boxes, ballots that were part of the vote had been destroyed, making it impossible to continue with the vote.”

The violations were so blatant the U.S. government filed the labor complaint; the vote was rescheduled in August, and confirmed the ouster of the old union.

For almost a century, Mexican unions have been largely a sham, with sold-out leaders guaranteeing low wages that drained manufacturing jobs out of the United States. Mexican auto workers make one-eighth to one-tenth of the wages of their U.S. counterparts, spurring a massive relocation of auto plants to Mexico.

The old-style union bosses were ruthless in threatening or allowing companies to fire dissident workers and often decided union votes with thugs, show-of-hand votes or gunplay.

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