The Reagan administration's budget-cutting has claimed a new casualty: the budget cutters themselves.

The budget for fiscal 1982, which begins in just eight days, is undergoing its fifth revision and the folks at the Office of Management and Budget are just plain tired--and getting further and further behind in their other work.

"There's a saying in OMB: 'the same old tired horses get fresh new riders,' " an OMB careerist noted. Except for a brief respite in August, there has been no letup for the OMB staff since January, when the Reagan team replaced the Carter team and threw out the completed Carter budget.

Yet for all the fatigue, there is also a sense of exhilaration, of doing something, even if that something consumes weekends.

OMB Director David A. Stockman "wants more numbers than any director we've ever had," a middle-management type noted. "That means we have had to produce those numbers time and time again. We've had to get permission to take Sunday off."

Normally at this time of year, budget examiners are busy sorting through the budgets of the various departments and agencies for the next fiscal year--in this case 1983--to see how closely they followed guidance letters that OMB sends out.

Those guidance letters sometimes go out as early as June, but this year they haven't even left OMB. At some point, this administrative logjam has to be broken because the president is required by the Budget and Accounting Act of 1921 to submit his budget 15 days after Congress convenes in January.

"OMB is a very conservative place with lots of traditions that have just been knocked for a loop," one budget examiner noted. "How can we complain about agencies' being late when we're three months late with policy guidance?"

Individual budget examiners, the heart of the OMB review process, have had little opportunity to visit the field and study government programs, something both they and their supervisors say is needed. OMB has spent only three-fourths of the $427,000 it planned for travel this year.

"One of the strengths of a good examiner," a division chief said, "is that he doesn't just rely on the agency or the department. The best ones use a variety of resources. The pace has held people to their desks much longer than we would like and has forced them to deal with the agencies more than we would like."

OMB has been more visibly involved (through Stockman) in the political process of enforcing the administration's will on Capitol Hill than at any previous time, oldtimers claim. That means OMB has become less of a reviewer and more of an advocate, a role that disturbs some traditionalists. "If OMB makes all the decisions, that ruins the analytical ability the president must have," said a former OMB staffer who retains close ties to the budget office.

"We have become more producers of fast information rather than more thoughtful analysis and review," said an OMB insider.

All this does not mean that people at OMB don't like their jobs or that the republic is coming to an untimely end because the budget office is out of gasoline. Morale is generally described as good and the turnover rate is about the same as usual, according to the personnel office.

"The virtue of this administration is that the policies are absolutely clear," a senior OMB careerist said. "Don't forget you have the pent-up frustrations of getting dumped on by the Carter administration for four years."

Furthermore, even though OMB is far behind the traditional schedule, there is a feeling that the traditional schedule is less important now than it was under Carter.

"This administration," said a career budget officer for one of the departments, "has done a better job of having political officers attuned to the president's philosophy. The result is that decisions are being made at the top levels early; there's going to be very little review" in the traditional sense.

Under Carter, another departmental budget expert said, the presumption was that if there were a disagreement with OMB, the secretary could fix it with the president. "Now the shoe is on the other foot. The burden of proof is on us, not on OMB," he said.

"In the Carter administration, our secretary would look at that letter and say, 'If that's a McIntyre number, ignore it,' " a reference to Carter budget director James T. McIntyre Jr. "Nobody says that about a Stockman number."