The transition team studying federal personnel policy for Ronald Reagan has uncovered a number of "difficulties" in one of the president-elect's most frequent campaign promises: a freeze on federal hiring.

In an initial report finished yesterday, Reagan's transition staff at the Office of Personnel Management outlined alternative courses the new administration might take to achieve a reduction in the federal workforce. Transition officials say prospects for a freeze are unclear, despite Reagan's campaign declaration -- a standard line in his stump speech -- that he would put a "complete" freeze in place within 24 hours of his inauguration.

Reagan was not the first presidential candidate in recent times to promise a federal hiring freeze to help prune government spending. Jimmy Carter made a similar promise when he ran for the presidency in 1976. Carter eventually did institute a modified freeze which is still in place.

Part of the problem, however, is that the federal workforce has not been growing as fast as presidential candidates like to suggest. At the end of the Truman administration, there were about 16 federal employes for every 1,000 Americans. Today there about 13 federal workers per 1,000.

To cut federal employment, Reagan in the campaign talked about a rule under which government agencies could not hire new people to replace those who leave. Many personnel experts consider such a freeze to be bad management, and the transition report reflects, the experts' doubts.

Donald J. Devine, a codirector of Reagan's personnel management transition group, said the initial report does not recommend any particular course of action. But he said the report "lays out some of the difficulties with a total freeze . . . taking a look at some generally suggested ideas about difficulties with it and suggesting some options to a total freeze.

Without discussing specifics, Devine noted that "there're all kinds of selective freezes you could use." He said there are "thousands of ways" to cut federal employment other than an immediate ban on new hiring.

Domestic policy advisers at the Reagan transition office say possible approaches include mandating cuts in the workforce of certain agencies to offset an increae in staff at offices considered critical. Another proposal is a call for a gradual reduction in employment rolls -- an executive order, for example, directing all agencies to reduce job slots by 10 percent over a three-year span.

Reagan has not said how much he wants to reduce federal employment. Randy H. Hamilton, a public administration scholar in California who has been advising Reagan on personnel policy, has said an appropriate goal would be a 10 percent cut.

Personnel and management experts recite a long list of problems with the freeze that Reagan proposed during the campaign. Alan K. Campbell, director of the Office of Personnel Management, echoes the consensus view when he says a total job freeze "is the worst way to cut federal employment."

The personnel people say total freezes are hard to enforce because it almost always becomes necessary to exempt certain agencies -- the Pentagon, the FBI, the Federal Aviation Administration's air traffic controllers. Gradually, they say, the list of exemptions grows to the point that the "freeze" effectively melts.

A freeze prohibiting replacement of employes who quit also tends to produce a top-heavy government, personnel people say, because most of the turnover in government employment is among lower-level workers such as secretaries and receptionists. The result is a government full of highly paid executives who cannot get their studies typed or their telephones answered.

Finally, some students of personnel policy believe a freeze slows the normal attrition of federal employes because it makes workers more cautious and less inclined to leave a safe job.

On the other hand, some of the president-elect's political advisers think he should institute a total hiring freeze, at least for a short time, to prove he will live up to his campaign promises and to demonstate a commitment to cutting federal spending.