Fourth generation

1978

1978 brought a downsizing of the Grand Prix and the other A-bodies. This version of the A-body also received some sheet metal revisions in 1981. The 1978 GP was about a foot shorter and 600 pounds lighter than the 1977 model with an overall length of 200 inches (5,100 mm) and a 108-inch (2,700 mm) wheelbase.

For the first time in Grand Prix history, a V8 engine was not standard equipment. In order to meet Corporate Average Fuel Economy (CAFE) mandates set after 1973-74 energy crisis, a Buick-built 231 CID V6 was standard equipment on the base model (formerly the Model J) and two versions of the Pontiac 301 CID V8 (Chevy 305 V8 in California) were optional. The luxury LJ model came standard with the 135 hp (101 kW) 301 V8 with two-barrel carburetor while the sporty SJ was powered by a 150 hp (112 kW) 301 V8 with four-barrel carburetor. A floor-mounted three-speed manual transmission was standard equipment with the V6 on the base model and the three-speed Turbo Hydra-Matic automatic was optional. Turbo Hydra-Matic was standard on LJ and SJ models and base models with either of the optional V8 engines. Standard seating choices by model included a notchback bench seat with cloth or Morrokide vinyl in the base GP, a pillowed velour cloth notchback bench seat in the LJ or Strato bucket seats in cloth or Morrokide in the SJ. The Strato buckets were optional on the base GP and a 60/40 split bench was optional on both base and LJ models. Viscount leather upholstery was available with bucket seats on SJ models.

1979

A new crosshatch grille and revised taillight lenses were the only appearance changes made to the 1979 Grand Prix. The same models, base, LJ and SJ continued as before as did the basic engine lineup including the 231 cubic-inch Buick V6 standard on base and LJ models, the 135 hp (101 kW) 301 cubic-inch Pontiac V8 with two-barrel carburetor that was optional on both of those models, and the 150 hp (112 kW) 301 V8 with four-barrel carburetion that was standard on the SJ and optional on the other models. Transmissions remained the same as before with the three-speed manual standard with the V6 engine on the base model and automatic transmission optional. The automatic transmission was standard on LJ and SJ models and all models when a V8 engine was ordered. Again, the Pontiac V8s were not available in California , where they were replaced by Chevy 305s rated at 140 and 160 hp (119 kW). A new and one-year-only option this year was a four-speed manual transmission available with the 301 four-barrel or two barrel V8 on all models. Only 232 4 speed/301 V8 cars were built.

1980

The 1980 Grand Prix returned to a vertical bar grille and featured new taillight lenses with "GP" logos. Automatic transmission was standard equipment on all models and the two-barrel 301 Pontiac V8 was replaced by a new 265 cubic-inch V8 rated at 125 hp (93 kW). The Buick 231 V6 and the four-barrel version of the Pontiac 301 V8 were carried over from the previous year as was the Chevy 305 V8 offered in California.

1981

A minor reskinning of the sheet metal for improved aerodynamics marked the 1981 Grand Prix along with a new grille design and revised tail section. The sporty SJ model was dropped and a new ultra-luxurious Brougham series was now the flagship of the Grand Prix line. The Brougham models came standard with all power options, a plush cloth interior similar to the full-sized Bonneville Brougham and a half roof vinyl top with coach lamps. The base and LJ models continued as before. All models now came standard with the Buick 231 V6 with the 265 cubic-inch Pontiac V8 available as an extra cost option (Chevy 305 V8 in California ). The 301 V8 was discontinued and a new option this year was the Oldsmobile-built 350 cubic-inch Diesel V8, which was not often ordered due to high cost of around $700 and poor reliability. The year 1981 was also the last for Pontiac Motor Division to offer its own V8 engine due to an emerging GM corporate engine policy that determined Pontiac would build only four-cylinder engines and Buick only V6 engines, leaving Chevrolet and Oldsmobile to build V8 engines for most GM cars and trucks, while Cadillac would produce its own aluminum-block V8 that debuted in 1982. From 1982-on, all V8-equipped Pontiacs were equipped with Chevy or Olds engines.

1982

The 1982 Grand Prix was a virtual re-run of the 1981 model with no appearance changes to note. No gasoline-powered V8 engines were offered this year (in the U.S. only - Canadian GPs were available with the Chevy 305 V8 as an option in '82), leaving only the standard 231 cubic-inch Buick V6, a larger Buick 252 cubic-inch V6 and the Olds 350 Diesel V8. The A-body line became front-wheel-drive, leaving the rear-wheel-drive midsize platform as the G-body. The downsized four-door Bonneville was now related to the Grand Prix. The automatic climate control option was also dropped in 1981, leaving just a manual climate controls on all models. Also most 1982 models had a two tone interior.

1983

1983 Grand Prix models specifically had no hood ornament and trim, and no rear trunk lock cover. One significant engine change to note was the 252 V6 was discontinued and the gas-powered V8 returned after a one-year absence (on U.S. models) in the form of a 150 hp (112 kW) Chevy 305. 1983 also marked the end of the LJ series, as the LE model would be added in 1984.

1984

Some minor changes and revisions marked the 1984 Grand Prix, including a new octangular Pontiac hood ornament, gauges with orange needles and red markings (previous 1978-1983 Grand Prix gauges had white needles), a T-shaped console shifter, an updated bucket seat design, as well as a wood-grain plate above the glove box (previous 1978-1983 Grand Prixs used a black plate). A new optional four spoke steering wheel was also available. The base and Brougham models continued as before but the LJ was replaced by a new LE model. Same engines continued as before including the Buick 3.8 liter (231 cu.-in.) V6, Chevy 5.0 liter (305 cu.-in.) V8 and Olds 5.7 liter (350 cu.-in.) Diesel V8. A new option this year was the Turbo Hydra-Matic 200-4R four-speed overdrive automatic available with the 305 V8 for improved highway gas mileage.

1985

For 1985, Grand Prix's now included a new checkerboard grill design, as well as a optional two tone paint schemes with a fading body stripe. New taillights with an octangular GP logo also debuted. 1985 marked the last year for the flat rear deck panel in the interior, as by 1986 laws mandated cars to have a third brake light installed. New rectangular digital ETR stereo system options were introduced and replaced the dial pushbutton stereos. Some rarer options specific for the 1985 Pontiac Grand Prix include a factory rear spoiler, rare aluminum turbo finned wheels, and a full size spare tire. The standard engine for 1985 was the 110 horsepower (82 kW) Buick built 3.8 liter (231 cu.-in) V6 with a 150 horsepower (110 kW) Chevy 5.0 liter (305 cu.-in) V8 optional. The 5.7 liter (350 cu.-in) Olds Diesel V8 was dropped from the option list.

An ad for the '85 GP promoted the fact that its instrument panel still used dials for gauges. It was highlighted by a question similar to one long used in advertisement for Dial soap since the late 1950s, "Aren't You Glad We Use Dials. Don't You Wish Everybody Did?"

1986

An updated taillight design with three sections was the only major change to the 1986 Grand Prix. A new 2+2 model was offered for homologation of an Aerocoupe body for NASCAR competition, as Chevrolet had released the Monte Carlo SS Aerocoupe in 1986 as well. 2+2 specific pieces are an aero nose, bubble rear glass and a fiberglass trunk lid with integral spoiler. All 2+2 models were fully loaded and came equipped with a corporate 305 four barrel, 200-4R 4 speed automatic transmission and 3.08:1 rear axle ratio, silver paint with 2+2 decals and striping, & 15X7 steel rally II wheels. Approximately 1225 Grand Prix 2+2's were built in 1986.

1987

The 1987 Grand Prix was basically a rerun of the '86 model aside from the discontinuation of the 2+2 model. The same three models were continued including base, LE and Brougham. Engine offerings again included the standard Buick 3.8 liter (231 cu.in) V6 or optional Chevy 5.0 liter (305 cu.in) V8.