Last Monday's column, which warned of the long delays that new retirees face before they get their first full pension check, brought in lots of mail. All of it was from retirees who say the gloom-and-doom picture we painted wasn't gloomy enough. The column advised those about to retire to have enough money saved up to pay rent, buy food, etc., until their full civil service retirement checks start coming in. We said the delay could be many months.

To illustrate the problem, the column used several examples of persons who retired last summer and who still are waiting for their first check or for full checks, which will arrive after examinations of records and the necessary paperwork have been completed.

More than 60 persons wrote in, saying they have been retired longer and have waited twice as long for checks as the retirees in our "horror story" examples. From a former high-level fed:

". . . Upon reading your column in Monday's Post . . . I do not wish to appear unreasonable, but I retired on doctor's orders from Interior in February 1980 and now, 9 1/2 months later, have not received my full monthly retirement check, nor even a wallet card with retiree number.

"To the credit of the Office of Personnel Management, a lovely voice-on-the-phone, Kit Ingles, has seen to it that I have received estimated partial checks each month. . . . The problem, the former official says, is that the government is having difficulty tracking down, confirming and computing his service with a now-defunct agency, and with the Marine Corps. He says Ingles is a "kindly, efficient OPM employe who restores one's faith in the federal establishment. Unfortunately, there aren't enough like her in other agencies to help with growing backlogs of retirement paperwork.

"So those 'kids' who retired in August and still haven't received their pension checks have nothing on this ol' boy," says the ex-Interior aide.

Officials think 25,000 or more persons may retire between now and Jan. 18. That will further swamp retirement processing procedures that already are overloaded. And the more complicated your records are -- military service, breaks in service, moves between agencies, etc. -- the more likely it is that your check will be delayed.

Federal and postal workers who retire after Jan. 18 will not be able to take advantage of the 7.7 percent annuity increase that went into effect last Sept. 1. A new law eliminates the "look-back" feature effective Jan. 19. That is why so many persons will be quitting during the next three weeks.

Many workers, and their personnel offices, are confused by the look-back benefit. It is great, but not as great as some people think. Here is OPM explanation:

"While employees who retire before that date will get the look-back, the advantage in doing so may be less than is usually assumed. The actual difference in an annuity computed with and without the look-back will rarely be the full 7.7 percent that was granted in September, because higher salaries and longer service have increased annuities since September 1, the date used under the look-back formula.

"For example, a 30-year employee at Grade 5, step 5, with a current salary of $13,902 would receive an annuity of $581 a month under the look-back computation. The same employee retiring on Jan. 19, when the look-back has been eliminated would," the OPM explanation says, "receive $564 a month. A 30-year employee retiring at GS 11, step 5, would receive $1,064 with the look-back or $1,034 without, and a 30-year employee retiring at GS 15, step 5, would receive $2,109 with the look-back, or $2,047 without it.

"The look-back makes a difference of $17 to $62 a month for the employees in these examples. Although this is a real difference, the employee considering retirement needs to weigh it against other aspects of retirement, including such things as the often significant reduction of income from salary to annuity and the new optional life insurance (up to five times salary) that will be available to those on the payroll April 1, 1981."

OPM says that would-be retirees also "need to consider that even if they retire in time to get the look-back, they will still receive only a portion of the next cost-of-living increse due on March 1, 1981."