A local union has put a host of prominent tech companies on notice that the drivers who ferry their employees to and from work want to organize.

The Teamsters sent letters last week to the CEOs of Amtrak, Apple, eBay, Genentech, Yahoo and Zynga informing them that their contract shuttle bus drivers would like to join the union and urging them to show their support, said Rome Aloise, international vice president and secretary-treasurer of Teamsters Local 853.

By unionizing, the shuttle bus drivers stand to gain better pay and benefits, as well as relief from a split shift that forces them to drive routes in the morning and evening with no pay in between, Aloise said. The drivers work for Compass Transportation, a South San Francisco-based company that has agreements with the tech companies.

“These tech companies are going to have to step up and pay more money so these drivers can have some shot at a decent life,” he said.

The bid to unionize more shuttle bus drivers, first reported by USA Today, comes amid an escalating debate in Silicon Valley over the gulf between handsomely paid tech employees and the legion of contract workers who serve them lunch, guard their campuses and drive them to and from work — without any lavish perks.

The Teamsters gained a foothold in the valley in November, when Facebook’s shuttle bus drivers, who work for Loop Transportation, voted to join the union. The vast majority of the roughly 120 drivers who drive for Amtrak, Apple, eBay, Genentech, Yahoo and Zynga have signed petitions and authorization cards indicating that they would also like to join the union, he added.

With the Facebook vote top of mind, Aloise said he is hopeful that Compass will agree to recognize the union. If the contractor declines, the question will probably be put to the drivers for a vote overseen by the National Labor Relations Board.

“We’ll prevail either way because they have got the example of the Facebook people going through the same thing and standing up,” Aloise said.

A spokesman for Compass, which is owned by Transdev, did not immediately respond to a request for comment.

Aloise said the Teamsters wrote to the tech companies Friday and have yet to receive a response. A Genentech spokeswoman wrote in an email that the company was aware of the union effort.

“Genentech believes that the issue is between Compass and its drivers,” she said. “Genentech has a long history of excellent working relationships with both union and nonunion contractors, and we will fully respect whatever decision is made by the drivers.”

Spokeswomen for Yahoo and Zynga declined to comment. Amtrak, Apple, and eBay did not immediately respond to requests for comment.

Shuttle buses have become a popular offering for tech companies catering to young employees who want to retire to hip San Francisco after a day of work in the valley. Though contractors abound, Loop and Compass have most of the business, Aloise said.

The Teamsters are in the midst of negotiating a contract with Loop for the Facebook drivers, Aloise said. After the process is finalized, Aloise said, the Teamsters will most likely turn to another Loop client: Google, whose fleet of “Google buses” has been cited as a symbol of economic inequality in the Bay Area.

Aloise said the Teamsters hope to achieve standardized wages and benefits for drivers across the valley, though the timing of shifts may be handled differently from company to company.

Contact Julia Love at 408-920-5536; follow her at Twitter.com/byJuliaLove.