Six weeks from now, the last bastion of the fully assumable mortgage -- the VA home loan -- will give way to the federal government's latest attempt to rub out loan fraud.

Yet, at the same time Congress was cracking down on transfers of loans insured by the Veterans Administration before adjourning for the new year, it was also liberalizing the harsher assumption rules for loans insured by the Federal Housing Administration. Those rules were set in 1986 by the Department of Housing and Urban Development. Even after the modifications, however, the new FHA policy is still designed to "provide some of the protections we were looking for in the assumption transactions," according to John J. Coonts, FHA's director of single-family housing.

The new VA and modified FHA rules represent the government's latest response to what some believe is a persistent loan fraud problem. "We were concerned that the freely assumable mortgage encouraged unscrupulous people to use straw buyers to complete the sale when they could not do it in a straight forward way," Coonts said.

In some cases, sellers have unloaded homes by refinancing them with a VA or FHA loan, which an unqualified borrower could immediately assume without pausing for a credit check. In the event the loan went into default shortly thereafter, the government agencies were often left holding the home, which might not have been worth as much as the outstanding loan on it.

Coonts said that loan assumptions account for an "inordinate" percentage of the 1.1 percent of FHA loans that go into foreclosure. However, Keith Pedigo, the VA's director of loan guaranty service, feels the assumption problem has been overstated because only about 12 percent of the VA loans in foreclosure as of six months ago were held by transfer owners.

"We think the foreclosure rate is low because most assumptions involve equity because the loan has been on the books for some time," whereas a veteran does not have to make any down payment when the loan is first obtained, Pedigo said.

The new VA rules go into effect March 1. No VA home loan closed as of that date can be assumed unless the buyer undergoes the same scrutiny that the original borrower did. The minimal $45 transfer fee will be replaced then by a funding fee equal to one-half of 1 percent of the loan balance plus a processing fee of up to $500.

President Reagan is expected to sign the new housing bill, possibly next week. Under that law, new FHA mortgages will become freely assumable to owner-occupants 12 months after origination of the loan, a reduction from the prevailing 24 months. The new law also limits the seller's liability to have to repay the loan in the event the new borrower defaults to five years from the date of the transfer, instead of leaving the seller liable until the loan is paid in full.

A buyer may still assume an FHA loan that is less than a year old, provided a credit report and income verification convince a lender that the borrower is credit-worthy.

FHA's new credit approval policy does not affect the 4 million-plus loans closed prior to Dec. 1, 1986.

Investors wishing to assume a post-1986 FHA mortgage are dealt with more severely than borrowers planning to live in the homes. An investor still must win approval for the loan when the assumption occurs any time during the first 24 months of the loan, as is the current practice. Under a provision that takes effect when Reagan signs the housing measure, an investor must pay down the loan to 75 percent of the value of the house before taking title to the property, unless the original borrower is willing to remain legally liable for the loan. Considering that many FHA loans are obtained with as little as a 3 percent down payment, the investor may need to produce quite a bit more cash to pull off the deal, Coonts said.

The five-year cap on seller liability for the loan also applies to investor assumptions.

While the federal government has given substantial attention to assumable mortgages lately, home buyers here have given the loan feature short shrift, primarily because it is hard to beat the current market rates of 10 percent to 11 percent on new financing.

Pam McCoach, a Fairfax real estate agent with ERA VanMetre Properties, said, "At the moment I would not say that an assumption for the majority of buyers is the main thing they are looking for. With the interest rates where they are {new loans} are workable for many people."

The current situation, McCoach said, is in sharp contrast to when interest rates were higher. "To assume a loan at a lower rate that would not escalate with the conveyance of the property was certainly of prime interest then," she said.

Yet, assumptions with few strings attached are still sought by investors, the self-employed, borrowers who cannot wait for six weeks for a loan to close and those with fluctuating incomes that can't stand up to a credit review. "There are always persons who, for cash or credit or income reasons, have difficulty getting a loan," explained Lewis F. Smith, a loan officer with First Chesapeake Mortgage Inc.

Consequently, homes with assumable loans often sell faster or sometimes for cash, according to Mary Fruscello, division vice president of real estate finance for the National Association of Realtors. "The premium is a function of how large the loan is with respect to the selling price of the home, because the older it is, meaning the less balance there is, the less advantage there would be to having it," she explained.

Few home buyers, however, are likely to consider the potential of an assumable loan later as a selling tool when securing new financing to buy a home, according to Robert M. O'Toole, a staff vice president with the Mortgage Bankers Association of America. "They may consider it as one of the factors, but they're more interested in rates," he said.

Despite the new tests borrowers must meet to assume a VA or FHA mortgage, the government-backed loans are more readily transferable than is another mainstay of the mortgage market, the conventional fixed-rate loan. With rare exception, conventional loans become payable in full when a house is sold.

There was a time, however, when virtually all mortgages were as freely assumable as the VA loan was prior to the latest change. In the early 1970s, a buyer could literally step into an owner's shoes, preserving the same interest rate and repayment schedule without any attendant paperwork.

But when interest rates started climbing past 6 percent as the decade wore on, conventional mortgage lenders started enforcing the previously ignored "due on sale" clauses found in most loan documents, according to Robert J. Engelstad, vice president for mortgage standards with the Federal National Mortgage Association (Fannie Mae). Despite the hue and cry from borrowers that lenders were running roughshod over a long-standing property right, homeowners lost when the Supreme Court ruled against them and subsequent federal legislation bolstered the lenders' position in the early 1980s.

With the latest changes for FHA and VA loan assumptions, government-insured mortgages are on about an equal footing with the conventional adjustable-rate mortgage, which also requires a credit check as a condition of assumption. However, when a borrower elects to convert an ARM to a fixed-rate mortgage -- an option available on many newer adjustable loans -- the financing becomes unassumable, warned John E. Hemschott, director of home mortgage standards for the Federal Home Loan Mortgage Corp. (Freddie Mac).

Harder to categorize is the assumability of jumbo mortgages, also referred to as nonconforming loans because they exceed the $168,700 limit on loans sold into the secondary mortgage market. "The problem is that they're all tailored {differently each time a lender offers such loans} and the lenders offering jumbos tend to offer them and pull out {of this niche of the lending market}, offer them and pull out," said NAR's Fruscello.

Fruscello suggested that buyers interested in homes with nonassumable jumbos negotiate with the lender. "Although he may not have any luck, he's in a better position than a conforming borrower is, particularly in this market because most loans generated here are considered to be high-quality product," Fruscello said. "The lender may be very eager to keep the loan on the books" and so approve the assumption.