The UAW has unleashed a full court press in recent days on social media and in its plants to convince its members that work at General Motors to vote in favor of a proposed four-year contract that gives all workers an $8,000 signing bonus and raises for nearly all workers.

The union’s outreach on social media on Monday occurred as several thousand UAW members at five GM plants in three states were voting on the new national contract.

Workers at GM Flint Assembly, Flint Metal Center, Arlington Assembly, a powertrain plant in Bay City, Orion Assembly and Toledo Transmission are scheduled to vote through tonight on the proposed, four-year agreement.

UAW leaders are hoping workers at those plants will provide momentum for ratification prospects after workers at two plants delivered mixed results over the weekend. Voting results from those plants are not expected until late Monday night or Tuesday morning.

A rejection of the agreement would be a major setback for the UAW, which already saw its image tarnished when workers at Fiat Chrysler Automobiles rejected the first contract that the UAW recommend.

UAW Vice President Cindy Estrada held a conference call Saturday afternoon with top local officials, urging them to encourage members to support the deal.

Estrada and other UAW leaders encouraged elected UAW local officials to use social media and walk through their plants to talk about the contract’s $8,000 signing bonuses, raises for all workers and improved health care for workers hired over the last eight years, according to a source familiar with the phone call who was not authorized to speak about it.

Union leaders are worried that the recent rejection of the first agreement with FCA set a dangerous precedent, according to a person familiar with Saturday’s conference call who was not authorized to talk about it publicly.

UAW elected leaders, such as Barry Campbell, who is chairman of UAW Local 598 in Flint, are telling members that the union must always balance wage and benefit gains with the ability of the company to compete and add jobs in the U.S.

“GM had several demands, also your bargaining team had some very tough decisions to make to secure our investment for job security, and also to make economic gains for all members,” Campbell told workers who build heavy duty pickups at Flint Assembly in a Facebook post. “Was it everything we wanted? No, but I’m very confident we took GM to the edge with a long and tiring fight.”

Over the weekend, a majority of workers at UAW Local 31 in Kansas City, Kan. voted to reject the contract over the weekend while workers at UAW Local 652 in Lansing voted in favor of the agreement as did members of UAW Local 174, a customer care and parts center in Ypsilanti, which voted 76% in favor.

To be ratified, a majority of 52,700 workers must vote yes. Voting ends Friday.

While union leaders are hopeful of passage, officials are also concerned about complaints that workers at four component plants will not see their wages rise to parity with workers at assembly, powertrain and stamping plants. Some skilled trades workers have expressed unhappiness that they may not be eligible for a $60,000 retirement incentive.

On Saturday’s conference call, GM union leaders discussed the need to communicate details of the contract more effectively than it did in the first round of ratification voting at FCA which workers rejected, forcing the two sides back to the bargaining table. The FCA agreement was modified slightly with a higher signing bonus for veteran workers and a pathway for wage equality between workers hired before and after October 2007. Workers ratified it in a second vote.

The UAW posted a video Sunday night featuring members of the national bargaining committee on the “UAW GM Talks” Facebook page.

“We have active workers that hire in making less for working 40 hours a week than some of our retirees make,” said Todd McDaniel, chairman of the bargaining committee and chairman of UAW Local 362 in Bay City. “Some of our retirees have put in more years and have a little bit higher pension. “Does the company have the money? Yes. Do our members deserve raises? Yes. But there is only so much. Can we get it all and still maintain jobs? No.”

“We can only get so much without driving them over the border.”

If the new contract is ratified, all workers would receive an $8,000 signing bonus and a raise. Entry level production workers currently paid between $15.78 and $19.28 per hour would see their wages increase to between $17 and $22.50 per hour and would eventually earn about $29 per hour.

Workers hired before 2007 would receive 3% raises in the first and third years of the contract and 4% lump sum bonuses in the second and fourth years of the agreement.

One of the most controversial aspects of the proposed agreement is to pay workers at the automaker’s GM Components Holdings LLC a lower pay rate than other workers. A group of about 3,400 hourly workers at several GM parts plants with one to four years of seniority would be paid $16.25 to $19.86.

Workers already at the top of that wage scale would get 3% wage increases annually and a 3.7 percent in the final year of the agreement. That means a worker already at the top pay would get $2.52 raise over the four years to about $22.40 an hour at the end of the four years.

“It’s frustrating because we get treated differently,” said Chuck Bonaffine, 47, who works at a GMCH plant in Rochester, New York told the Free Press. “We are very disillusioned.”

On Facebook, hundreds of workers have argued that the UAW has allowed GM to create a new tier of workers just as it has closed the gap between other tiers. The UAW and GM say workers at the parts plants do different work than regular production workers and GM must be able to compete with suppliers who pay workers less for similar jobs.

Meanwhile, Vicki Hale, president of UAW Local 31, sent a Facebook message warning members that GM is unlikely to make a better offer if this contract is rejected.

“Our union leadership team has bargained one of the best contracts I have seen in the last three national agreements,” Hale said in the message. “We didn’t get everything we proposed and we never get everything we propose, however our international bargaining team bargains for the greater good of all GM Unite UAW members.”

Contact Brent Snavely: 313-222-6512 or bsnavely@freepress.com. Follow him on Twitter @BrentSnavely.