The new GM full-size bodies for 1971, at 64.3 inches front shoulder room (62.1 inches on Cadillac) and 63.4 inches rear shoulder room (64.0 inches on Cadillac) set a record for interior width that would not be matched by any car until the full-size GM rear-wheel-drive models of the early to mid-1990s. Following this remodel, the Sixty Special remained basically unchanged through 1976, save for front and rear-end refreshenings. The car shared styling cues with the lesser models. The most dramatic of these changes was the addition of rectangular headlamps in 1975 along with a completely new grille. This configuration also marked the end of the traditional large-size Cadillacs, as 1977 would see a dramatic down-sizing of all full-size Cadillacs except for the Eldorado.
For 1971, the lineup was trimmed down to just one Sixty Special model, the Sixty Special Brougham. It still rode on an exclusive 133.0 in (3,380 mm) wheelbase, but with all-new sheet metal and a distinctive roof design. The formal new roof was clearly reminiscent of Bill Mitchell's original 1938 Sixty Special, with individually framed, rounded-corner side glass (outlined by a thin chrome bead). Also new on the vinyl top were C-pillar mounted opera lamps and a thick B-pillar - all of which heightened the limousine effect. To complete the "custom-body" look, the front and rear side doors had a narrow body filler panel between them. Despite the formal new look and higher levels of luxury, sales dropped slightly from last year, down to 15,200 units.
Engine performance began to decrease with EPA restrictions on tailpipe emissions and grams per mile emissions requirements, forcing gear ratios to taller and taller ratios, dropping to as low as 2.41:1. A new common frame/suspension design was introduced in the latest generation Sixty Special which was also used in other GM full size cars. While the other GM divisions used a front-steer setup (steering linkage in front of the engine crossmember), all Cadillac RWDs retained the 1961-vintage front suspension (rear steering linkage, eccentric cams in the steering knuckle in lieu of shims, strut rods attached to the framerails for caster adjustment). Rear suspensions were now driven by the Pontiac-designed 8 7⁄8-inch ring-gear 10-bolt salisbury live axle.
A new trailer towing package was added allowing larger trailer loads to be pulled. Coupled with heavy duty cooling, 3.23 gearing, high output 80 amp large frame alternator and heavy-duty THM400 transmission, the long wheelbase was ideal to pull trailers weighing up to 7,000 lb (3,200 kg).
1972 was Cadillac's 70th anniversary. One of the few changes on the 1972 was the addition of a chrome molding around the rear window. Sales were a robust 20,750 units at a base price of $7,585. The 1972 Sixty Special Brougham weighed in at an impressive 4,858 pounds shipping weight (over 5,000 pounds curb weight). Standard equipment included rear-seat reading lamps, automatic level control, and dual-comfort front seats. A wide range of upholstery was available in nine colors of "Sierra" grain leather, four colors of "Matador" cloth, a combination of "Matador" cloth and leather, a "Minuet" fabric in three colors, or a plush "Medici" crushed velour.
The 1974 model year saw the introduction of the "Air Cushion Restraint System" (airbags) activated when the car was hit from the front only. Hidden in the steering wheel, and passenger side of the instrument panel, were instantaneous-inflating nylon bags designed to prevent front seat occupants from hitting the windshield during a frontal collision. The option replaced the glove box with a lockable compartment under the dashboard. During the mid-seventies this option never caught on and was dropped from the option list after 1976. A digital clock was added.
When the Sixty Special Series was temporarily retired in 1977, the Cadillac Fleetwood Brougham took its place as Cadillac's most luxurious owner-driven large sedan model through 1986.