Cadillac shrank its lineup in 1977, deleting the Calais line and making the popular Coupe De Ville and Sedan De Ville the entry level models. At the same time, all mainline Cadillacs were reduced in size by 8 to 12 inches in length and 3.5 inches in width, though interior space was the same. Most Cadillacs lost hundreds of pounds of weight and received a new 180 bhp 425 cid V-8, while the Seville continued with the Oldsmobile-based V-8.

The Eldorado continued on in the same enormous size, though powered by the 425 V-8 and shedding 100lbs. The 1977 Cadillac Eldorado changed little from the year before. Even without the convertible in the lineup, sales remained strong.

Base price was now $11,187, but the Eldorado Custom Biarritz package could add $1760. It featured a chrome spear along the fender line, a padded Elk Grain vinyl roof, limousine back window, and Sierra Grain leather upholstery. A sunroof or available AstroRoof boosted the price even further.

The Special Custom Cabriolet package continued for the Eldorado Coupe, with a “halo” half vinyl roof that featured a chrome bar across the top. Behind it was padded vinyl and ahead of it could be a sunroof.

The 1977 Eldorado was available with optional leather interiors and a bench front seat with folding center armrest. Automatic climate control was standard, along with power door locks, a 6-way power adjustable seat, an AM/FM stereo radio, and steel-belted radial tires.

Popular options included airbag, padded vinyl roof, power sunroof, AstroRoof, tilt/telescopic steering column, cruise control, intermittent wipers, remote trunk release, rear window defogger, AM/FM stereo with tape player, AM/FM stereo with CB, tinted glass, heated front seats, and automatic headlight dimmer.

Calendar year production rose 16 percent to a record 358,487 total as the division marked its 75th anniversary and delivered its 6 millionth car, a Seville bound for a California customer. Everybody had a pretty good year, however, and Cadillac slipped back to 10th place in the U.S. market.