Some American workers here have charged that the legislation drawn up by the Carter administration to implement the Panama Canal treaties is full of gaps affecting their futures and does not provide all the administration promised them.

At the same time, both U.S. and Panamanian officials here assigned to smooth the Oct. 1 Panamanian takeover of the 10-mile-wide Canal Zone fear that congressional opponents of the treaties will block, or seriously delay, the legislation's passage.

What seemed little more than an abstraction to many during the tedious years of negotiations and bitter Senate debates last spring now appears to be just around the corner.

Despite the drawn-out steps outlined in the treaties, which do not give Panama total control over the waterway or provide for the with-drawal of U.S. troops here until the year 2000, the Panama Canal Zone itself will cease to exist at midnight on Sept. 30.

At that moment, the famed manicured lawns and residential areas of American towns like Balboa and Cristobal will become Panamanian property. Their police, fire and postal services, their railroad and their ports, will be administered by the Panamanian government within a 30-month transition period stipulated by the treaties.

The Panama Canal Co., which has run the canal since it opened in 1914, will self-destruct. Some, but not all, of its employes and operations, including navigation and maintenance, will pass to a new Panama Canal Commission, composed of five U.S. and four Panamanian delegates, or to the U.S. Defense Department.

At least 4,000 U.S. jobs will vanish as functions are turned over to the Panamanian government. Private commercial businesses set up years ago on U.S. territory will become foreigners operating on foreign soil.

How all this upheaval will be managed is supposed to be spelled out in the pending U.S. legislation -- 64 pages of sections and subsections -- and implemented with Panamanian cooperation.

But as the transfer date approaches, there is growing apprehension here that somehow, something will go wrong.

Some Canal Zone workers feel something already has. According to Jim O'Donnel, president of Local 14 of the American Federation of Government Employes, the 850 workers he represents have been "sold down the river" by the legislation.

In writing the legislation last summer, the administration solicited suggestions from Local 14 and other unions.

"They wanted our ideas," O'Donnel said in an interview, "and we broke our back to come up with the documents."

Among the 19 detailed suggestions the AFGE local submitted was a lowering of age and seniority retirement formulas for those workers, such as canal pilots, whose jobs would be transferred to the commission, and eventually to Panama.

O'Donnel also asked for an increase in retirement annuities and the guaranteed continuation of U.S. government benefits, such as commissary and PX privileges, for those formerly employed by the canal company or under special contracts whose jobs were transferred to the Department of the Army.

"Not one of our proposals was adopted," O'Donnel wrote in an angry letter to Army Secretary Clifford Alexander. "The alleged consultation process," the letter said, "is little more than a foolish charade."

"I must now use whatever avenue is open to me outside your office to achieve the goals of the canal workforce," said O'Donnel.

Possible avenues include trying to change the legislation through Congress, or threatening to support those legislators who would like to kill it altogether. Although the administration maintains that the treaties will take effect with or without the legislation, hardcore congressional opponents are still pressing the issue in court and are attempting to recruit disenchanted Canal Zone workers to their cause.

"Let your voice be heard again!" Rep. George Hansen (R-Idaho) told Zonians in letters addressed to "occupant" and mailed last fall by the American Conservative Union.The letter, which contained an appeal for funds, noted that "it is still possible to save the Panama Canal."

Like many Zonians, however, Bill Homa, whose father started a construction business here 47 years ago, feels fighting against the treaties is a lost cause.

"I've given money to the [opponents] in the past," Homa said, "but our position now is that we live by the laws of the United States."

Still, Homa finds the legislation both vague and inadequate for his company's needs.

Homa said he has no idea if his company, now a Canal Zone partnership, would be better off incorporating in Panama, or in the continental United States. In Panama, he may be required to pay not only Panamanian taxes but Panamanian benefits -- including a 13th month of annual pay, a month's vacation and full medical and retirement benefits -- to his Panamanian workers.

Yet if the bulk of his contracts remain with the U.S. Defense Department on remaining bases, he will be requred under U.S. law to pay his workers the $2.65 U.S. minimum wage, rather than Panama's 75 cents.

"Nobody's getting any answers," Homa said, "because nobody knows."

Although large numbers of Americans began to leave the Canal Zone in 1976, when the number of resignations ran 50 percent above normal, the often predicted post-treaty exodus has not occurred.

Canal company public relations director Frank Baldwin said most people "don't want to say what they're going to do. They're just waiting."

In a company survey several months ago, nearly 44 percent of 3,400 U.S. employes responded to questions on their post-implementation plans.

Among those whose jobs are eliminated by the transfer, less than a quarter said they would immediately resign or retire. Two-thirds of the respondents said they would accept "any reasonable job offer" in another field, presumably from the new commission.

Among those whose jobs' iunction is transferred to the Panamanian government, however, more than half said they would not accept any shift to a new post under Panama.

Most Americans' attitudes, Homa said, are that "if they [Panama] treat me all right, I'll stay. I'll give it a chance. But the first time something goes wrong, they'll have my resignation."

According to Edwin Fabrega, in charge of Panama's end of the transfer, Panama is more than willing to keep American professionals on the payroll -- at their same salaries -- in those jobs, such as port operations, where professionals are needed.