The Treasury, under intense pressure from Chrysler Corp. and other beleaguered firms, plans to liberalize regulations governing the sale of corporate tax shelters so that companies facing the prospect of bankruptcy have a chance to sell their investment credits and depreciation rights.

The revised ruling, which is expected to be issued today, will prompt widespread revision of a host of pending tax sale deals.

Under a grandfather provision in the 1981 tax bill, companies face a Nov. 13 deadline to convert equipment purchases made as far back as Jan. 1 into paper transactions known as "leases."

These leases, in turn, become the vehicle for unprofitable companies to sell unuseable tax breaks to profitable firms looking for ways to reduce their obligations to the Internal Revenue Service.

Treasury Secretary Donald T. Regan said yesterday he plans to revise regulations issued Oct. 20 that such highly marginal firms as Chrysler contended would kill their chances of participating .

"I wanted to make sure that we played fair with all sectors of the economy," Regan said.

Despite the seemingly restrictive regulations, Ford Motor Co., which also is running in the red, with losses of $713 million so far this year, has been able to sell all its tax breaks on equipment purchases for the entire year to International Business Machines Corp.

The two companies refused to disclose precise details, but they said IBM paid Ford somewhere between $100 million and $200 million for the depreciation rights and investment tax credits on total equipment valued at somewhere between $500 million and $1 billion.

According to Treasury officials, the revised regulations will reduce significantly the danger to the profitable company of facing a tax penalty if the unprofitable firm goes bankrupt in the the middle of the lease term.

Under the October regulations, the "lease" in effect would be declared invalid in the event of a bankruptcy where the court trustee refused to honor the terms of the lease. Ernest S. Christian Jr., an attorney representing Chrysler and a wide range of other firms, said at that time that the regulations would "make the leasing process impossible" for corporations "that do not have excellent credit."

The regulation to be issued today in effect declares that the lease will remain valid in the event of involuntary transfer of the leased property in foreclosure proceedings so long as the original creditors agree to accept the lease. This means that a profitable company can protect its interests by requiring all creditors on the property to be leased to agree before the lease is signed to honor the lease.

Christian was unavailable for comment, but Treasury sources said it is their understanding that the revisions will permit Chrysler to enter into lease arrangements.

Under terms of a lease, a company like Chrysler would sell tax rights on equipment to a profitable firm and then lease the equipment back. The profitable firm would be able to take the 10 percent investment tax credit and depreciation. The lease, under most terms, would set rental payments at a rate exactly equal to the cost of paying off the cost of the equipment, and at the end of the lease the unprofitable firm would have the right to "buy" the equipment back for a nominal cost.