Some newly minted Port Authority Police Department captains are already scrambling for a new job — their old one.

The PA promoted 10 lieutenants to captain in July. But nine months later, at least some of them are far from pleased with their new assignments and want to be demoted back to the lower rank they once held, sources told The Post.

The group is upset over sweeping new changes that PA management intends to impose on their benefits package as part of a larger, cost-cutting initiative that would affect all non-union employees, insiders said.

“[Higher-ups] are trying to cap longevity raises, and they are asking for more in medical-insurance contributions, vacation days and uniform allowances,” one insider said.

The 10 new captains were summoned to a staff meeting with PAPD supervisors Friday and presented with the “laundry list” of proposed work rule changes that would reduce each captain’s overall compensation package by an estimated $10,000 to $15,000 annually, sources said. The meeting was volatile, the sources added.

“[The new captains] were not happy. A lot of them are going to be looking to head for the exits,” one insider predicted.

There are currently 75 lieutenants in the PAPD, and while captains earn a higher base pay, the agency has traditionally found it difficult to convince many of them to accept a promotion because of the sweet deal they now enjoy.

Lieutenants earn from $113,097 to $124,097 after five years. They also frequently reap tens of thousands more in yearly overtime.

By comparison, captains are paid between $145,000 to $153,000 but don’t get overtime and have no union to represent them.

If a mass exodus of captains was to occur, PA management would likely resist it, as there are now only two open slots available.

“There’s nowhere to put them,” a source noted.

But captains looking to jump ship are expected to cite the case of George Santiago, a 19-year veteran who until recently headed the Staten Island bridge command. About a month ago, Santiago asked to be voluntarily demoted to his past rank of lieutenant, a request that was approved by PAPD Superintendent Michael Fedorko.

Still, one management official insisted that Santiago’s request did not have anything to do with his fear that his benefits would be slashed but was based upon a “personal situation” that made it difficult for him to carry out his added responsibilities as a captain.

Lisa MacSpadden, a PA spokeswoman, said details of the agency’s proposed cost-cutting measures affecting the captains and others would be released later this month, when the results of an audit by Navigant, a consulting firm, are publicly discussed.

A Navigant audit has called the PA a “dysfunctional agency” and documented how authority staff members enjoy lush salaries and benefits.

“At its next board meeting on March 29, the Port Authority Board of Commissioners will consider a range of sweeping reform recommendations called for in the Navigant audit report released in February,’’ MacSpadden said in a written statement.

“Significant changes, including revisions to employee benefits, are on the table for review, and we will have further comment at that time.”

Promotion commotion

What do lieutenants get:

* Earn between $113,097 and $124,097

* Can net tens of thousands of dollars more annually in overtime

* Are unionized

What do captains get:

* Earn between $145,000 and $153,000

* Don’t get overtime

* Aren’t part of a union