The federal retirement program, untouched in the budget that was approved by the House, would undergo major temporary and permanent changes in the budget plan that has been okayed by the Senate.

The differences between the two plans -- differences that affect the payments workers make to their pension plan and raises due retirees next January -- will have to be ironed out when Senate-House conferees work out a compromise for the fiscal year that starts in October.

Here is the Senate proposal:

* Federal workers would not get a pay raise next year, and longevity pay increases (worth 3 percent) would be delayed a year. Those are the increases that are paid automatically to most U.S. employes, based on time in grade and satisfactory job performance ratings. Pay increases due postal workers would not be affected because of their union contract.

* Government and military retirees, along with persons under Social Security, would not get a cost-of-living adjustment (COLA) next January. Raises for them would resume in 1987.

* Federal workers would begin putting 9 percent of their salaries into the civil service retirement fund in January 1987. Postal workers would be hit with the higher contribution rate next year. Both groups now contribute 7 percent of salary to the pension fund.

* Cuts in federal employment would be made over the next three years and could trigger hiring freezes or layoffs in some agencies.

* Benefits for survivors of federal-postal workers who die in the future would be reduced to conform to the survivor benefit system under Social Security.

The House plan is much less drastic, as far as government workers and retirees are concerned. It would:

* Freeze federal pay next year, but would not make any change in the longevity pay system.

* Permit federal, military and Social Security beneficiaries to get full COLAs in 1986.

* Make no change in the federal retirement contribution rate.

* Reduce overall federal employment through attrition and reductions in government contracting-out activities.

Obviously, the House budget plan looks better to most U.S. workers and retirees, particularly in the area of COLAs and retirement contributions. Federal and postal unions will lobby for the House plan.

The key differences in the overall budget are defense spending, and Social Security-retiree payments.

The Senate plan would allow Pentagon spending to keep pace with inflation, while freezing all retiree COLAs for one year. The House plan freezes defense spending, but permits full COLAs. Whatever happens on those two issues will determine the type and depth of cuts that will be applied to civil service programs.