Industry lobbyists seeking to reverse a 1976 tax crackdown on Americans working abroad intensified their efforts yesterday with a new study showing that the resulting higher taxes hurt exports and increase unemployment.

The study, compiled by Chase Econometric Associates Inc., concluded that the tightened tax treatment for overseas Americans has cut U.S. exports by 5 percent and has lost 80,000 jobs and $6 billion in revenues for the Treasury.

The document was made public yesterday as part of a stepped-up effort in the Senate to push through legislation to provide larger tax exemptions for Americans working abroad.

The U.S. and Overseas Tax Fairness Committee Inc., the principal lobby group for the legislation, his hoping to tack the measure onto a general tax cut bill, if one is proposed later this year, or on some other legislation.

The effort, centered on a proposal by Sen. John H. Chafee (R-R.I.), so far is opposed by the Carter administration, but there is a split among various agencies and departments on the issue.

The Treasury consistently has opposed the new legislation on grounds that it is an attempt to undo the crackdown enacted in the 1976 Tax Reform Act. However, Special Trade Representative Reubin Askew says he favors the higher exemptions.