Walt Michaels, the New York Jets' head coach for six seasons, announced his retirement yesterday, 17 days after his NFL club's appearance in the American Football Conference championship game, the 14-0 loss to the Miami Dolphins.

Joe Walton, the Jets' offensive coordinator since leaving the Redskins' staff two years ago, is considered the leading candidate.

Michaels, 53, is the eighth NFL coach to leave his job following the 1982 season. "I have spent 32 years in this game and I've enjoyed them all," the former all-pro linebacker said in a prepared statement. "But in that time, I have never taken a vacation and have never spent enough time with my family. Now I think it's time that I should . . . "

Michaels just may have been pressured to retire. His temper outbreaks after playoff games in L.A. and Miami apparently did not sit well with owner Leon Hess, according to some of his players.

Michaels had an overall record of 39-47-1 in regular-season games and was 2-2 in playoffs . . .

ABC has decided against making its instant replays available to on-the-field officials at the 18 United States Football League games it will televise this spring and summer, according to play-by-play commentator Keith Jackson. "We feel it is not our position, as the one presenting the game, to provide instant replays for decision-making within the game," said Jackson, here on a 12-city tour for the network, whose two-year commitment to USFL coverage starts March 6 (including Channel 7's Tim Brant with sideline interviews) . . .

Joe Theismann, in Philadelphia to receive the Maxwell Football Club's Bert Bell Award as the year's outstanding pro player, sounded like Joe Gibbs in asserting that the Super Bowl champion Redskins know their limitations. "Next year this team will not be overpowering," the quarterback said. "It realizes its capabilities and we have to work at it." Theismann said he couldn't sleep the night of the Pasadena triumph because he was afraid somebody would take his Super Bowl ring. So, he related, he rode around in a car, rolled down the windows and shouted, "We're the world champions!"

Herschel Walker, the Georgia junior accepting the Maxwell as college player of the year, made it emphatic: track is his first love, he is not interested in NFL or USFL until he has had his sprint at the 1984 Olympics .