Dozens of Chicago Fire Department brass have warned that they’re prepared to resign their exempt positions and return to the rank-and-file in a squabble over pay and benefits — creating uncertainty over how the city would fill such a leadership vacuum.

The fire officials are seeking pension changes, expanded health insurance benefits and pay raises — and have been unable to persuade Mayor Rahm Emanuel and Fire Commissioner Jose Santiago to sweeten the pot for them.

But city officials say that would require a change in the state pension code.

“The city continues to have conversations with those exempt fire department staff who have expressed concerns about the state pension code, which is pending Springfield legislation,” said Julie Kaviar, a city spokeswoman.

Fire officials must retire at age 63. But exempt officials — non-union, senior staff — must pay for their own health insurance until they hit 65.

Exempt fire officials also lose pay perks, including vacation time, when they become exempt staff members.

In addition, the state pension code doesn’t allow exempt fire officers to earn pension benefits based on their current salary. Instead, their pension benefits are based on the lower salary of their most recent union-covered job.

All of that can result in a loss of thousands of dollars in pay each year for exempts — sometimes $20,000 or more, sources say.

Pending state legislation would allow exempt fire employees to earn a pension based on the pay for their current jobs. Many exempt officers are nearing retirement age and have signed a letter to the city warning they may return to the rank of battalion chief to improve their pensions and health insurance benefits before they leave the department, sources say.

One city source said Santiago was sympathetic to the exempt officers’ concerns, despite being unable to help. So far, none of the exempt officers has resigned and gone back to the position of battalion chief, “but it is probably just days away,” the source said.