The House early today approved, 236 to 169, a nickel-a-gallon increase in the federal gasoline tax to finance $5.5 billion a year in job-creating highway, bridge and mass transit improvements.

Then the House passed, 262 to 143, and sent to the Senate a four-year highway reauthorization bill that includes the gasoline tax increase and projects it would finance.

The gasoline tax is now 4 cents a gallon. The increase to 9 cents would take place April 1.

Despite a rare joint push by President Reagan and House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) for passage, the bill's fate appeared in some doubt for most of the more than 10 hours of debate as an unusual assortment of allies battled various provisions.

Opposition came from forces as varied as the trucking lobby, which opposed higher taxes on heavy trucks, and environmentalists, who feared the impact of new interstate highway construction.

As the debate extended into last night, the House approved strong new "buy-American" provisions in what appeared to be an indication of mounting trade protectionist sentiment in Congress.

Transportation Secretary Drew Lewis said he assumed that the administration would oppose the new "buy-American" provisions in the Senate and in a House-Senate conference on the bill. "We're basically not for 'buy-American' legislation," he said.

As the long debate opened, the administration offered two last-minute concessions aimed at rounding up wavering lawmakers.

The concessions, introduced by House Public Works Committee Chairman James J. Howard (D-N.J.), were aimed at assuring some of the biggest and most economically hard-pressed states that they will get -- as well as pay -- their fair share of the new six-year program costing about $30 billion.

One of the concessions would guarantee that all states get back at least 85 cents in highway grants for every $1 of taxes they contribute, which Howard said would add $420 million to the price tag of the measure. No state would receive less than it would otherwise have been entitled to, he said.

The other concession would allow financially strained states to defer matching-fund requirements, which range from 10 percent for interstate highways to 25 percent for secondary roads, although payment would be required within three to four years.

As many as eight states stood to gain from the first concession, and 17 from the second.

The concessions were approved by voice vote after a stronger proposal from Texas Republicans Bill Archer and Jack Fields, which called for a floor of 90 cents on the dollar instead of 85 cents, was defeated on a non-recorded vote of 31 to 8.

Although Howard said the concessions "eliminated practically all the opposition" to the spending part of the package, an unexpectedly close 197-to-194 procedural vote on rules for considering the legislation indicated widespread misgivings over several major financing features.

The strongest objections were raised to provisions that would raise non-fuel taxes paid on heavy trucks, which some lawmakers complained would not be fully offset by a trade-off that would permit larger, heavier trucks on interstate highways.

Some Democrats also voted against the rules because they wanted to jettison the gasoline tax increase in favor of a cap of $700 per taxpayer in the 10 percent income tax cut that is scheduled to take effect in July. The rules prevented a vote on the income tax issue.

On the vote to increase the gasoline tax, a majority of both parties voted for the increase, Democrats more heavily than Republicans. Among Democrats, 140 supported the increase, while 82 opposed it; on the GOP side, 96 voted for the increase, and 87 were opposed.

Among Washington area members, Reps. Steny Hoyer (D-Md.) and Frank R. Wolf (R-Va.) voted for the increase, while Reps. Marjorie S. Holt (R-Md.) and Stanford E. Parris (R-Va.) voted against. Rep. Michael D. Barnes (D-Md.) did not vote.

The measure, which Democrats view as part of their anti-recession job-creating effort even though the administration refuses to call it a jobs bill, would finance a variety of highway-related construction and repair projects.

The administration estimates that the legislation would create 320,000 jobs, and Howard said yesterday that the measure is expected to produce 335,000 new jobs within 90 days.

The administration has said it will have $5 billion to $6 billion worth of projects ready to go within 90 days.

However, some government as well as private economists have questioned whether the jobs gain will amount to much because of job losses that can be expected from the higher gasoline taxes.

The new program is part of a four-year authorization bill of more than $71 billion for highways and mass transit systems, and includes $16 billion for interstate highway completion work, $10.4 billion for repairs and $4.1 billion for mass transit, including subsidies provided through new grants to the states.

While the administration opposes continuation of transit operating subsidies and some other spending features, officials yesterday reaffirmed their support of the whole package and said they would work to cut some of the costs, including transit subsidies, in the Senate.

Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) said the Senate hopes to take up the measure Thursday. Asked if he thought it would help alleviate unemployment, Baker said: "It certainly won't solve the problem, but it's the best we can do in the lame-duck session."

House and Senate Democrats, however, are planning a second jobs package and there are increasing signs from Senate Republicans that they may accept at least some extra spending for jobs this year, even though Reagan has threatened to veto any further jobs legislation. Senate Appropriations Committee Chairman Mark O. Hatfield (R-Ore.) recently said some additional jobs money may come out of a Senate-House conference on a stopgap "continuing resolution" to fund the government through next spring.

This is the vehicle that House Democrats hope to use for another $5 billion jobs initiative. Senate Democrats are talking about trying to attach their jobs program to the highway bill.

In the debate over the gasoline tax in the House, Democrats and Republicans joined in describing the highway-related improvements that would be financed by the tax as essential and long overdue.

Among amendments that were approved, the House strengthened "buy-American" provisions of the measure to provide for domestic purchase of all steel, cement and manufactured products so long as they are made in sufficient quality and quantity in the United States.

Fifty percent of mass transit vehicles could be purchased abroad so long as they are assembled domestically. The vote in favor of these protectionist measures was 54 to 46.

The House also twice defeated efforts to deny Davis-Bacon "prevailing-wage" protections (often meaning union wage scales) for new jobs that would be created by the gasoline tax increase, and approved an amendment by Rep. Parren J. Mitchell (D-Md.) to require that minority contractors get 10 percent of the work authorized by the bill.

After the final vote, Secretary Lewis hailed the bill's passage, saying, "Although differences remain over certain provisions, we are pleased that the bill has successfully moved through the House . . . .The end result is a vital commitment to good roads, safe bridges and improved urban transit."