Working husbands still outearn working wives by a very large margin, but about 4.8 million American wives, representing almost 20 percent of women in two-paycheck marriages, earned more than their husbands in 1983, the Census Bureau reported yesterday.

The bureau reported that there were 26.1 million married couples in which both the husband and wife worked. In about four-fifths of these families, the husband made more than the wife, in part because three-quarters of the husbands worked full time year round, whereas only half the wives did.

But in 4.8 million families -- almost 20 percent of two-earner households -- the wife was the high earner.

In most of those families, according to the report, traditional patterns tending to make the husband the chief breadwinner were reversed or less pronounced.

For example, among those 4.8 million families, a higher proportion of women worked full time year round than men -- 3,496,000 to 2,364,000. In some cases the husband was disabled or unable to find a job.

Wives outearning their husbands also tended to be better educated. In the 4.8 million families where the wife earned more than the husband, only 646,000 of the women had not completed high school, compared with 1,043,000 of the men. And 2,077,000 of the wives had completed at least one year of college, compared with only 1,969,000 of the husbands.

Moreover, the figures show that in many of the cases, the women outearning their husbands were in executive, professional, administrative and managerial jobs but were married to men who were not.

Of the 4.8 million women outearning their husbands, 2,451,000 had no children under 18 years old and another 1,245,000 had children from 6 to 17. Only 1.1 million had children under 6.

In addition to the 4.8 million women who earned more than their husbands, another 2.2 million earned between 80 percent and 100 percent of what their husbands made.

Overall, the census study found there were about 42.2 million married couples in the country earning one or more paychecks. The bureau found that 39.9 million of the husbands in these families worked -- three-quarters of them year round and full time -- and that 28.4 million of the wives worked, 48 percent of them full time and year round.

The earnings of all working husbands averaged $22,980, more than double the $10,160 average for working wives, but these figures include part-time and part-year workers.

For those who worked full time year round, the gap was smaller, with husbands averaging $26,530 and wives $15,040.

The study found that where both spouses worked full time year round, the combined earnings averaged $39,390.