Montgomery County Executive Charles W. Gilchrist urged legislators from Maryland's wealthiest jurisdiction today to shed their traditional "defensive" strategy in the General Assembly and make an unprecedented appeal for $39 million in state funds for two major highway projects and new school construction in the I-270 corridor.

Because roads and classrooms have not kept pace with the rapid growth in the "upcounty" area near Gaithersburg, Montgomery is in danger of "losing the edge, the force that we have" as the state's leading magnet for high-technology and biomedical firms, Gilchrist said in a speech to members of the county's legislative delegation.

The county executive is seeking $14 million to widen Rte. 355 north of Gaithersburg and $11 million to improve Rte. 118 in Germantown, both heavily used commuter roads in the I-270 corridor. Gilchrist also asked for legislation providing $14 million to finance two new elementary schools and to modernize five schools.

County legislative leaders promptly endorsed Gilchrist's appeal but said it will be politically difficult to move the proposals through the House and Senate, where similar projects for other counties and Baltimore will compete for state funds.

One factor that could hamper Montgomery's proposal is its size, several legislators said. A $39 million package would be the single largest bonding request initiated by the county government, which in the last 10 years has sought and won $7 million in bonding projects.

"We will need divine assistance," declared Sidney Kramer, chairman of Montgomery's Senate delegation. "The county's in a crisis situation on expansion and growth, and these are legitimate projects. But that doesn't mean we'll have a sympathetic legislature."

However, House Speaker Benjamin L. Cardin (D-Baltimore) said he may support some special funding for Montgomery. "I'm open to it because their requests are reasonable. Montgomery County does have a special need."

The legislation will soon be introduced in the House and Senate, county lawmakers said.

Gilchrist said the state funds are crucial to Montgomery, which has reached the limit of its bond-issuing authority largely because of a six-year, $1 billion construction program he proposed this month. The requested construction money would come not from new categories of state aid but from a widely used government bonding program that "we seek to have carried out fairly," Gilchrist said.

This year, the state's bonding program will finance about $220 million in new construction, but because most of that money is earmarked for projects around Maryland, legislative leaders said it was unlikely that Gilchrist's entire request will be funded in 1985. A major competitor for construction funds is the University of Maryland, which is seeking $47 million to build a shock-trauma facility in Baltimore.

Sen. Laurence Levitan (D-Bethesda), the chairman of the legislature's Budget and Taxation Committee, said that because of limits on new construction funds, Gilchrist's plan "is really stretching it a little bit. I agree that the county's on the hook and the state ought to reimburse . . . but I think he may have gotten carried away."

Officials in the state transportation department also may be reluctant to endorse funding the costly road improvements because the two projects are not on the department's master construction list.

State Highway Administrator Hal Kassoff said his agency "agrees with the need for the new projects." But he added, "There are more worthy projects than we can fund at the moment." The state is scheduled to spend roughly $300 million for new and improved roads in Montgomery by 1990, Kassoff noted.

By his own account, Gilchrist's speech today marked a departure from the county's traditional strategy during the annual 90-day legislative session. " . . . We need to be pro-active" and campaign for new funding much harder than in the past, he said.