The Maryland House of Delegates approved the pay-back of $100 million yesterday to a Transportation Department trust fund -- money that will be used to cover the first payment to persons whose deposits have been frozen in Old Court Savings & Loan.

The House also voted to add an additional $29 million that the state reimburses to the trust fund. That money was used several years ago to cover emergency needs and never put back into the fund.

By a 125-to-8 vote, the House approved the pay-back, despite pleas from lawmakers from Western Maryland and Montgomery County who said the legislature was being steamrollered into a vote.

The $100 million transfer is a key element in Gov. Harry Hughes' plan to distribute up to $5,000 each to Old Court depositors by March 31. Future payments extending until 1989 are to come from the sale of Old Court assets.

The Baltimore thrift, where a run on deposits in May sparked the state's savings and loan crisis, is undergoing liquidation. It is one of four thrifts where deposits remain frozen.

The General Assembly has no power to vote on whether Hughes should use the trust fund to bail out Old Court because the governor is using the money under emergency executive powers.

Lawmakers, however, have the power to require the state to pay back the money to the trust fund.

The Senate approved a similar measure last week, but the House bill requires smaller payments to the trust fund over a longer period of time. A joint conference committee will have to resolve the differences in the two bills.