A House Judiciary subcommittee voted 4 to 3 yesterday to extend from seven years the time allowed for states to ratify the Equal Rights Amendment to the Constitution.

The controversy now goes to the full committee, where the outcome is less certain. Rep. Don Edwards (D-Calif.), chairman of the civil and constitutional rights subcommittee which voted the extension yesterday, said chances in the committee are "50-50" at this point. He estimated if the vote were held today it would be 16 to 18 against the extension. "It will take lots of work from back home," said Edwards, who expects a vote in about a month.

Both Edwards and Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) predict the extension would pass the House if it gets out of committee.

Edwards said the Judiciary Committee was "more conservative" than the House, but he would press for a vote even if it appeared the extension would lose, because extension is "ERA's only chance."

Edwards lost one of those votes yesterday, when Rep. Harold L. Volkmer (D-Mo.), who had appeared to be leaning toward extension, voted against it. "I'm not 100 perecent sure that what we're doing is constitutional," Volkmer said.

Extending ratitication from the time the amendment passed Congress in 1972 until 1986 might not meet the constitutional requirement that amendments be ratified "in a reasonable" amount of time, Volkmer said. He might vote for extension if the period were shorter.

Volkmer joined Reps. Caldwell Butler (R-Va.) and Robert McClory (R-Ill.) in voting against extension.

The deadline for ratifying ERA is March 22, 1979. At this point the amendment is three states short of the 38 necessary to make it part of the Constitution.

Supporters of ERA argue that the issue is still very much alive and debate should not be cut off by an arbitrary deadline. The deadline was adopted as part of the amendment, is not required by the Constitution and can be changed by a majority vote of Congress, they say.

Opponents of ERA say extending the deadline changes the rules in the middle of the game and goes against basic requirements of fairness.

The full committee expects an attempt to attach a rider to the extension that would allow states to rescind their ratification.

Idaho, Nebraska, Kentucky and Tennessee have already voted to rescind ratification, but the legality of rescinding has never been taken up by the courts. So far, no constitutional amendment containing a deadline for ratification has taken more than four years to be ratified.

Coupling permission to rescind with an extension is popular with many members of Congress as a way of pleasing both sides of the issue.

Some question exists as to whether a simple majority or a two-thirds vote of both houses would be needed to pass the extension. Edwards and others believe only a majority is needed since it does not change the substance of the amendment, but opponents of ERA contend the same two-thirds that is needed to pass a constitutional amendment would be needed to change any part of it.