The 85-ton Skylab, which still threatens to fall from orbit in 1980, was commanded last night to assume a new position, in an attempt to prolong its time in space.

Just after 8 last night, a commond was sent from Houston's Johnson Space Center for the 5-year-old space station to pitch upward 180 degrees, placing its two giant maneuvering gyroscopes in more direct sunlight during Skylab daylight hours.

Skylab was ordered to a new position because the space station's gyros responded 'erratically last month to commands from earth. Flight directors concluded that the erratic response was because the gyro lubricants were partially frozen.

"What the gyros did was hiccup instead of move right through the maneuver," said a spokesman for the National Aeronautics and Space Administration. "Tests show that the reason for the hiccups is probably that sunlight was not reaching the lubricants for them to flow freely through the hearings."

The 180-degree pitching maneuver was expected to take about 60 minutes, the time it takes for Skylab to travel two-thirds of the way around the world. By 9:30 last night, flight directors expected confirmation that the space station was in its new position.

The new position keeps Skylab in what engineers call a "minimum drag attitude," which means that the deterioration of its orbit will not accelerate. NASA officials say the space station has fallen three miles in the last three months, putting it 234 miles above the earth.

Keeping the gyros in perfect working condition means that flight directors can reposition Skylab whenever necessary to maintain its "minimum drag" The space station also can be maneuvered by firing its tiny thruster jets but flight directors want to save the thruster gas for the time astronauts in the space shuttle are expected to rendezvous with Skylab in 1980.

Plans call for the shutte to maneuver within a mile of Skylab, then for the astronauts to "fly" a $35 million rocket engine to Skylab, attach it, and boost the spacecraft into an orbit high enough to keep it in space.

At the rate it's falling now, Skylab will be down to an altitude of 150 miles in March or April of 1980. NASA figures the shuttle astronauts must reach Skylab before then because from that altitude there is no guarantee the Skylab could be raised high enough to keep it in space.

If the shuttle can't get to Skylab, the space station will be allowed to enter the earth's atmosphere where it would break up, spreading a trial of debris 3,000 miles long and 100 miles wide. As many as 400 pieces weighing up to 300 pounds a piece might survive the heat of friction with the atmosphere and strike the earth at speeds up to 200 miles an hour.