Bucking the trend of mergers between law firms, the major Cleveland and Washington firm of Jones, Day, Reavis & Pogue is splitting up.

According to lawyers in the firm, the split reflects major philosophical differences in the kind of firm the partners desired.

So far, none of the 140 lawyers in the firm's Cleveland office or the smaller Los Angeles office will be affected, but about 50 of the 82 members of the Washington office will split off to create a separate independent law firm.

The new firm's business will be builg around government contracts work, the specialty of many of the departing lawyers, including Eldon Crowell, W. Stanfield Johnson, Roger N. Boyd and Don Holmes.

The group that will remain with Jones, Day is committed to building a "national firm" with integrated operations, rather than the more autonomous operation those leaving wanted, firm sources say.

Staying in the Washington office are Erwin Griswold, former Harvard Law School Dean, and a number of former government officials including James T. Lynn, former director of the Office of Management and Budget and Housing and Urban Development secretary, and Donald I. Baker, former assistant attorney general in charge of the antitrust division.

"People like me really feel that we want to try to put together a firm that can serve the needs of any client in the country," says one of the lawyers who will be staying. "This means you have a firm with a broad range of capabilities and decent depth in each of them. It also requires a substantial amount of firm integration and a good management system."

Another element that was raised in the fray -- though not the most important -- was the issue of potential conflicts of interest. Some of the firm's partners argued that the firm's representation of many large firms in government contracts work increased the risk that the firm could be disqualified in a wide variety of general practice cases.