The G platform (also called G-body) is an automobile platform designation that General Motors used for its intermediate (mid-size) car lines. Adapted from the rear-wheel drive A platform, two versions of the G platform were produced; first from 1969 to 1972 and again from 1982 to 1988. While primarily associated with personal luxury coupes, the second-generation G platform underpinned coupes, sedans, station wagons, and coupe utility pickups. As with its A platform predecessor, the G platform was marketed by every GM division (with the exception of Cadillac).

The final American-market midsize cars produced with body-on-frame construction, the G platform would also become the final American rear-wheel drive sedan platform designed by GM in the 20th century. During its production, GM began to replace G-body vehicles with front-wheel drive vehicles from the A platform and the H platform, with the 1988 GM10/W platform serving as its ultimate replacement.

During the mid-1990s and 2000s, the G platform designation was revived, denoting GM front-wheel drive full-size and luxury sedans.

Use

1970s General Motors introduced the G platform designation for 1969, when Pontiac introduced the third-generation Grand Prix, which shifted its chassis from the full-size B-body to the A-body. Though using a two-door body, it was designed with a 118-inch wheelbase (two inches longer than A-body four-door sedans); the designation was also applied to the introduction of the Chevrolet Monte Carlo coupe, which used the 116-inch wheelbase of the Chevelle four-door sedan.

For the 1973 "Colonnade" redesign of the A-body line, the Grand Prix and Monte Carlo again shared underpinnings with the A-body line, replacing the G-platform underpinning with "A-Special". While sharing a similar formal-style roofline with the Oldsmobile Cutlass Supreme and Buick Century (later, Buick Regal), the Grand Prix and Monte Carlo again shared a longer 116-inch wheelbase with A-platform sedans.

For 1978, GM downsized its A platform model lines (in following the 1977 redesign of its full-size B and C platforms). Along with adopting a much smaller exterior footprint, GM ended its practice of using separate wheelbases for each bodystyle, adopting a 108-inch wheelbase for each model (with the exception of the Chevrolet El Camino and GMC Caballero). Internally, the A-Special coupe designation remained, applied to the Buick Regal, Chevrolet Monte Carlo, Oldsmobile Cutlass Supreme, and Pontiac Grand Prix; while again having a formal-style notchback roofline, each of the four model lines were styled differently from one another.

1982–1988 For 1982, GM redesigned and downsized the A platform again, shifting it to front-wheel drive. However, the new platform was not intended to replace the entire model family directly, so GM redesignated its remaining rear-wheel drive midsize vehicles under a revived G platform designation (including the quartet of G-Special coupes).

The introduction of the front-wheel drive A-body involved several model changes for each division. For Buick, the Century shifted entirely to the new platform, with the Regal adopting it station wagon and sedan (dropped in 1984 and 1985, respectively). Chevrolet gradually phased out the Malibu in favor of the front-wheel drive Celebrity; the Malibu coupe was dropped for 1982, with the entire line ending for 1983. Oldsmobile replaced its Cutlass sedans with the Cutlass Ciera, keeping its Cutlass Supreme sedans and coupes (along with the 442); the Cutlass Cruiser wagon moved to the A platform for 1984. Pontiac made would make several changes; while the Grand Prix was unaffected, the LeMans was dropped in the US (the Grand LeMans sedan and wagon continued in Canada through 1983). Pontiac also downsized the Bonneville for 1982 to the mid-size segment (utilizing the body of the Cutlass Supreme sedan).

For 1984, station wagons were introduced to the front-wheel drive A platform, leading to the discontinuation of G platform station wagons. For 1986, GM introduced its front-wheel drive H platform to replace multiple B platform model lines, leading Buick to drop its Regal sedan; Pontiac shifted the Bonneville to the H platform for 1987.

1987 marked the final full year of production for the G platform; the Monte Carlo and Cutlass Supreme were produced for a shortened 1988 model year, with both ending assembly at the end of 1987. While the El Camino and Caballero were retired without replacement, the Regal, Cutlass Supreme, and Grand Prix were moved to the front-wheel drive GM10 platform (today, W platform). For 1990, Chevrolet debuted its GM10 vehicle, introducing the Chevrolet Lumina to replace the Monte Carlo and the Celebrity under a single model line.

Vehicles +Model nameModel yearsConfigurationPredecessorSuccessorNotesBuick Regal1982–1987Buick Century (A platform RWD)Coupe: Buick Regal (W platform) Sedan: Buick LeSabre and Buick Electra (H/C platform FWD)

Wagon: Buick Century (A platform FWD)For 1982, Buick expanded its Regal line (sold only as a coupe since 1978) by repackaging the previous Buick Century sedan and station wagon under the Regal model line. For 1984, the Regal station wagon was discontinued, following the introduction of the front-wheel drive Buick Century wagon (becoming the final Regal station wagon until 2018); a year later, the Regal sedan was also retired to accommodate the downsizing of the Buick LeSabre and Buick Electra.

The G platform Regal was sold with high-performance turbocharged Grand National and T-Type variants. Limited-production GNX is most powerful version of G platform.Chevrolet El Camino1982–19872-door coupe utility pickup Chevrolet El Camino (A platform)N/ABuilt on longer-wheelbase (117 inches) chassis, shared only with GMC Caballero. Shares front bodywork with Chevrolet Malibu (including El Camino SS); rear bumper and tailgate are shared with Malibu station wagon. Final generation of the model line; functionally replaced by Chevrolet S10 compact pickup truck. Chevrolet Malibu1982–1983Chevrolet Malibu (A platform)Chevrolet CelebrityFor 1982, Chevrolet introduced the Celebrity as the successor of the Malibu, leading Chevrolet to drop the 2-door Malibu from the G platform. The front fascia was restyled with quad headlamps (looking more like the Impala/Caprice) After 1983, the G platform Malibu was replaced entirely by the Celebrity. Chevrolet Monte Carlo1982–19882-door coupeChevrolet Monte Carlo (A platform) Chevrolet LuminaFor 1983, the Chevrolet Monte Carlo SS was introduced, featuring a reshaped front fascia used by Chevrolet for stock-car racing. For 1986, Chevrolet introduced the LS with flush-mounted headlamp lenses and the SS Aerocoupe, featuring an aerodynamically-curved rear window.

The Monte Carlo was produced for a shortened 1988 model year (ending in December 1987); the model line was replaced by the 1990 Chevrolet Lumina (along with the Chevrolet Celebrity). GMC Caballero1982–19872-door coupe utility pickup GMC Caballero (A platform)N/ABuilt on longer-wheelbase (117 inches) chassis, shared only with Chevrolet El Camino. Shares nearly its entire bodywork with the Chevrolet El Camino, itself derived from 1982-1983 Chevrolet Malibu station wagon. The GMC Caballero Diablo is the equivalent to the El Camino SS. Only generation of the model line; functionally replaced by GMC S15/Sonoma compact pickup truck. Oldsmobile Cutlass SupremeOldsmobile Cutlass Supreme Classic1982–1987 1988 (Cutlass Supreme Classic)2-door coupe 4-door sedanOldsmobile Cutlass Supreme (A platform)Sedan: Oldsmobile Cutlass Ciera, Oldsmobile Cutlass Supreme (W platform) Coupe: Oldsmobile Cutlass Supreme (W platform)For 1982, Oldsmobile began to phase in the front-wheel drive Cutlass Ciera as the successor of its four-door Cutlass Supreme line, as it retired its lower-trim Cutlass and Cutlass LS sedans; Oldsmobile marketed the Cutlass Supreme and Cutlass Supreme Brougham on the G platform. The two-door Cutlass Supreme range saw fewer changes, continuing its namesake version alongside the luxury Brougham and touring-oriented Calais and Salon trims. As a muscle car, Oldsmobile introduced the limited-edition Hurst/Olds for 1983 and 1984, replacing it with a revived Oldsmobile 442 for 1985. For 1988 (produced through December 1987), the Cutlass Supreme Classic was produced, offered only as a two-door coupe. At the beginning of 1988, the Cutlass Supreme adopted the GM10/W platform, introducing a four-door sedan for 1990. Oldsmobile Cutlass Cruiser1982–19835-door station wagonOldsmobile Cutlass Cruiser (A platform RWD)Oldsmobile Cutlass Cruiser (A platform FWD)The Cutlass Cruiser nameplate was introduced for 1978, applied to its midsize wagons with and without wood-paneled exterior trim. For 1984, Oldsmobile shifted the Cutlass Cruiser from the G platform to the A platform, giving the name to the Cutlass Ciera station wagon. Pontiac Bonneville Pontiac Grand LeMans1982–1986 (Bonneville) 1982–1983 (Grand LeMans)Pontiac LeMansPontiac Bonneville (H platform)For 1982, Pontiac retired the LeMans name in the United States, with the Grand LeMans marketed in Canada for 1983. The model line was replaced by the front-wheel drive 6000, but Pontiac marketed a G platform sedan as the body of the LeMans was given a minor facelift and repackaged as the Bonneville for 1982. In downsizing the model line from the B platform to the G platform, the Bonneville became the 4-door sedan counterpart of the Grand Prix, with a 5-door station wagon offered through 1983 (replaced by a 6000 station wagon for 1984). For 1987, Pontiac shifted the Bonneville to the front-wheel drive H platform. Pontiac Grand Prix1982–19872-door coupePontiac Grand Prix (A platform)Pontiac Grand Prix (W platform)For its redesignation on the G platform, the Pontiac Grand Prix saw no major changes - with the exception of the Bonneville replacing the LeMans as its four-door counterpart. In contrast to other "G-Special" coupes, the Grand Prix was not offered with a high-performance variant. For 1986, the Grand Prix 2+2 (see below) was introduced with an aerodynamically-enhanced exterior to homologate the model line for stock car racing.

Performance applications General Motors G platform vehicles were some of the last cars to follow the traditional muscle car formula (intermediate-size, rear-wheel drive coupe with powerful V8 engine), remaining popular as the mid-size segment was shifting towards front-wheel drive. Buick, Chevrolet, and Oldsmobile each sold a significant performance variant of their model line, including the Buick Regal Grand National, Chevrolet Monte Carlo SS, and Oldsmobile 442. +Model nameYears produced PowertrainNotesBuick Regal Sport CoupeBuick Regal T-Type/Turbo TBuick Regal Grand National turbocharged V6Buick introduced the turbocharged V6 for the Regal Sport Coupe in 1978 (serving as the replacement for the 455 V8), with a 175 hp 4-barrel version offered in 1982. The Regal Sport Coupe was last offered in 1982, with the Grand National developed as a limited-edition option package commemorating Buick's stock-car racing success; of the 215 produced for 1982, fewer than 50 were fitted with the turbocharged engine from the Sports Coupe. For 1983, the Regal Sport Coupe was replaced with the Regal T-Type. Along with the turbocharged V6, the T-Type also included upgraded suspension, brakes, and steering, alloy wheels, and blackout trim; the interior was fitted with bucket seats and a console-mounted shifter.

After skipping 1983, the Regal Grand National was made a regular-production option package for 1984. Along with the chassis and interior upgrades of the T-Type, the turbocharged V6 was made standard. In contrast with the T-Type, the Grand National was produced with an all-black exterior (with no Regal badging nor a hood ornament).