Originally Posted by Nas Escobar
78-81 are "A" bodies, but are considered part of the "G" body platform range because of the name switch in 1982, when the A body was supposed to replace what became the G body because at the time the G body was going to replace the B body, hence the 1982 refresh that made the cars look more like the Caprice. Reality of it was that the A body supplemented the J body as alternatives to the failed FWD X body (Citation). The W body effectively replaced the G body, which is what they wanted to do with the FWD A body. By this time, most of the G bodies were coupes, sedans were phased out in 1983, leaving only the coupes. The 1980's Cutlass Supremes (all Olds were Cutlass in the 1980's except for the Firenza, 88, 98, and Toronado)
Anyways, I'm not sure where this thread is going, but if you want to know about GM platforms, their platforms usually began in relation to another platform... for example the 1st N bodies were closely related to the J bodies up until the 1997 redesign (with the Malibu). This is mostly true in which the J and N both had V6's, both had a 5x100 bolt pattern, both were compact cars. The L body (Corsica, before the Malibu) was developed separately but is practically an N body. When the Malibu was developed, the project was merged with the Alero and Grand Am (the only name to survive, both Acheiva and Cutlass Calais were names used on the Alero's predecessors) and lost most of the J body's distinctions whereas the J body became strictly 4 cylinder with no wagons in 1995.
The W body was its own platform, perhaps the biggest one developed during the Roger Smith era. The goal was more or less to have 70's A body (Chevelle, Lemans, Skylark, Cutlass) volume. Ironically it was supposed to be a mid size platform, and it's evident in the first FWD Grand Prix, Regal, Cutlass Surpeme, and Lumina but when the Impala came around, it grew bigger to become a full size platform. Even though the new Impala is bigger than the W Impala, it was the de facto full size car for GM. Only the H body was bigger than the W body.
Here's where it gets confusing... GM has always had different full size platforms. Historically, the B body is actually the smallest full size car frame they had. The C was bigger than the B body and was for Buick, Olds, and Cadillac. When GM switched to FWD, the C body shrunk to H body proportions, essentially making them the same car. It didn't help that the cars started to look the same and people started thinking that the cars were upper trims of each other in the brand lines. Ironically, both C and H were developed concurrently and the H was meant to replace the B body.
Cadillac on the other hand got a new platform for the Seville, which Ironically was based on the Nova. The K body Seville of 1975-1980 was essentially based on a muscle car, because the X body which carried the Nova, Apollo (Later Skylark), Ventura (later Phoenix) and Omega shared components with the F body (Camaro/Firebird), notably the front end. A lot of X body owners swap F body parts, and they fit with no real modifications.
When the C and K switched to FWD, the K essentially grew in size whereas the C shrunk and was similar to the H. It stayed like this until the Aurora came out. At this point (1995), the B body had a new body on the same 1977 frame (and as such, you can put a box caprice on a bubble frame), the K body grew essentially defeating the purpose of the Seville and became Deville sized. It then essentially became the whole Cadillac lineup excluding the Fleetwood/Brougham but including the Eldorado, which had been GM's first FWD car (along with the Toronado). The Eldorado was on the E platform, but merged with the K platform, more or less becoming the 2 door Seville in the 80's with the Buick Riviera tagging along with it when it too downsized and the Olds Toronado which at this point somehow ended up looking like the N body Calais. The C platform was left with the Park Ave and 98, and then there's the mess with the H platform.
The H platform was intended to replace the B body - which before 1984 included the Bonneville, Caprice, Impala, Delta 88, and LeSabre. After 1981, the Bonneville downsized again becoming the G body. Then it grew again when the 88 and LeSabre went to the H body. The Caprice was the only B body car and more or less merged with the former C body which became the D body. The Fleetwood/Brougham were essentially longer Caprices.
At this point all these cars were separate platforms. The K and related E, the C and the H.
1995 rolls around and the Aurora came out, on its own platform. This platform was named "G" and was the top of the line, even better than Caddy's K platform.
Then 2000 comes. At this point, the H body cars were old, being in the market with the same body for 8 years. Olds lost the 88 and 98 and what remained all merged with the Aurora. At this point, the K, C, and H platforms were all the same thing because all the cars moved to the G platform but still labeled as their original platform letters in the VIN. Therefore a 2000 Bonneville is the same thing as the Deville but they're still considered H and K bodies respectively. The G platform outlived the brand it was developed for, lasting 6 more years after the demise of Olds when the last cars (Lucerne and DTS) were replaced by nothing (some say the Lacrosse) and XTS.
Now, GM only has 5 platforms for cars. Delta and Epsilon, which stretches or shrinks depending on the car; Zeta, which is the RWD plaform, Alpha - which will replace Zeta and replaced Sigma (which in turn replaced the K platform), Gamma - which is the small car platform and then there's... the Y body. The only platform to go along unmolested since the C4 Corvette was introduced. This is the only GM platform that has kept the original naming nomenclature despite a C7 being nothing like a C4. The only thing that will interchange are the wheels.
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