Postal workers, thanks to collective bargaining and linkage with the inflation rate, are rapidly closing the pay gap between themselves and their white collar federal colleagues.

Currently, the average white collar civil servant earns $18,713. The pay average for half a million postal clerks, letter carriers and management personnel is now $17,072. And postal pay is moving up faster each month.

The favorable pay changes mean that the man or woman who delivers your mail, or sells you stamps at a post office window, now earns -- for the first time -- more than non-management counterparts at HEW, Treasury, VA, the Defense Department and most other "white collar" federal agencies.

Pay is one reason a growing number of young people who look to government for jobs are taking tough, physically demanding assignments with swing hours on postal loading docks, rather than 9 to 5 p.m. jobs in the Federal Triangle.

For years the average postal worker earned about the same as the typical clerical federal employe, or beginning professional. Now the typical clerk, carrier or mail handler enjoys a differential of about $2,000 a year.

The salary changeover began in the early 1970s. After a wildcat strike, postals broke away from pay linkage with the rest of the bureaucracy. Since the Post Office Department became a government-owned corporation, the U.S. Postal Service, it has been able to bargain bigger, better pay raises and fringe benefits than other civil servants who still depend on Congress or the White House to set the amount of their salaries and health insurance premiums.

Last year federal white collar workers (and military personnel) got a 5.5 percent pay raise even though the White House agreed that a raise of around 8 percent was more in line with reality.This year President Carter has granted federal-military personnel a 7 percent raise, effective Oct. 1. That is still short of the 10.4 percent federal pay raise that experts say is due rank-and-file bureaucrats.

During the same period, postal unions signed a new 3-year contract with the U.S. Postal Service that included a "no-layoff" clause, three pay raises and six very important cost-of-living adjustments during the period.

The first postal pay raise came in July 1978 and was for a flat $500 for each of the nearly 600,000 workers. The second raise this year, also in July, was a flat 3 percent. But the big difference was supplied by the postals' linkage to the living costs.

In November 1978 postal workers got a cost-of-living raise of $187. Then in May 1979 they got another adjustment, this one for $541 for each employee. Postal workers are due another COL raise in November that will be for at least $649. The final figure will be set when this month's consumer price index comes out sometime in late October.

Ironically, as pay for top postal executives and rank-and-file employes has gone up, salaries of middle management personnel -- mostly here and in big regional offices -- have remained fairly constant. Some postal employes in white-collar jobs in the headquarters operation say they are $2,000 or more behind their counterparts in other federal agencies.