WASHINGTON, Jan. 17--Secretary of Defense-designate Robert S. McNamara, who sold his Ford stock in a move to allay fears, discovered that fears persist--among the senators who must approve him.

Their concern focused on the problem of conflict of interest. While the Senate Armed Services Committee had no question about McNamara's sale of $1.5 million worth of Ford Motor Co. stock, two members questioned him closely today about what he is going to do with the money.

"I will be quite happy to modify the agreement any way you suggest," McNamara told Sen. Harry F. Byrd and the other members of the committee. He suggested that his lawyers could sit down with lawyers of Congress and work out a satisfactory trust fund.

Rickover Receives Medal

GROTON, Conn., Jan. 17--Vice Adm. Hyman G. Rickover stood on the bridge of the submarine Nautilus as she first sailed under nuclear power six years ago.

With 16 atomic submarines in service, Rickover stood again on the Nautilus today--the sailing's sixth anniversary--and received the Navy's highest peacetime decoration, the Distinguished Service Medal.

Pinning on the decoration, Secretary of the Navy William B. Franke said the fiery admiral was "largely responsible for making the dreams of nuclear power for ships come true."