They shuttle highly paid Facebook employees to and from the company’s headquarters in Silicon Valley, yet many say their pay is so low that they can’t afford to live in the area. Moreover, many complain that they start work around 6 a.m. and do not finish until 9 p.m., 15 hours later.

Now, some of these shuttle bus drivers, who get Facebook employees to work, are seeking representation by the Teamsters union. And, in a move to help make that happen, the union has written to Mark Zuckerberg, Facebook’s chief executive, asking him to intervene on the drivers’ behalf.

In a letter sent on Thursday, the top Teamsters official for Northern California urged Mr. Zuckerberg to press Facebook’s shuttle bus contractor to agree to bargain with the union on behalf of the 40 drivers who ferry Facebook employees to work.

“While your employees earn extraordinary wages and are able to live and enjoy life in some of the most exclusive neighborhoods in the Bay Area, these drivers can’t afford to support a family, send their children to school, or, least of all, afford to even dream of buying a house anywhere near where they work,” the Teamsters official, Rome Aloise, said in the letter.