I guess they refer to different body (chassis?) types, but can anyone simplify this a bit?

- FieroRumor

Do you mean as far as the actualy car it represents?

F-body is Camaro Firebird, W-body is Cutlass,Grand Prix, and a few others.G-body is the older Cutlasses and Monte Carlos(i.e. SS)

Go here, it will give you more info http://discussions.gmforums.com/index.php

Yup, it's the different chassis. Figure when they are designing the car, Chevy, Pontiac, Buick, etc. may all have their own version of the car, but it'll basically be the same car with only trim differences. So they designate that vehicle chassis with a letter.

F: Firebird, Camaro
G: RWD Monte Carlo, Grand Prix, Cutlass
W: FWD Grand Prix, Monte Carlo (?)
N: Grand Am, Alero, Malibu
Y: Corvette
P: Fiero
J: Sunbird/Sunfire, Cavalier, Cimmaron, Skyhawk
T: Chevette, T1000
B: Bonneville, Caprice (at least when they were RWD, not sure about now)

As far as answering your question... I don't think that the letters actually represent anything on the car..?

GM sets the letter I think.

Here is a good example of a classic "J" body style.

Some of them had special meanings (the meanings may have came later though)

Here's a complete list of the chassis designations

A - 64-80: RWD Cutlass/Skylark/Chevelle/LeMans/Malibu/Regal/Special
81-96: FWD Ciera/Century/Celebrity/6000
A Special - 68-80: RWD Coupe Monte Carlo/Grand Prix

B - 62-95: RWD Delta 88/LeSabre/Caprice/Bonneville/Roadmaster/Parisienne/Catalina/Impala,etc
92-96: Buick Roadmaster
94-96: Impala SS

The B-body has always been RWD, and ceased to be produced around December 14th, 1996. The B body Bonneville was discontinued in 1981 and then brought back as the Parisienne in about '84. 1985 marked the last year for Olds and Buick RWD B-cars, and the new for '86 FWD models were built on the 'H' platform, which closely resembled the FWD 'C' cars. B-body wagons continued past '85; Pontiac was the first to be discontinued ('90??), followed by Olds ('92), then Chevy and Buick early in 1996.
C - Dn-83: RWD 98/Electra 225
84-Up: FWD 98/Park Ave

D - Dn-96: RWD Fleetwood/Sedan DeVille/Limo
85-96: RWD Cadillac

When the 'C' cars went FWD in '85, the rear drive Cadillac Fleetwood Brougham (renamed only Brougham from '87 -'92) continued to be produced, and became the D-body.
E - Dn-94: Toronado/Eldorado/Riviera

F - 67-up: Camaro/Firebird

G - 78-88: RWD Sedan Cutlass/Regal/Malibu/Bonneville
95-up: FWD Aurora/Riviera
G Special - 81-88: RWD Coupe Cutlass/Regal/Monte Carlo/Grand Prix

I'm sure many Canadians would associate the '80s use of the Bonneville nameplate with the 'G' platform (4-dr), while 'Parisienne' would grace the Canadian B-body conterparts. The G body was renamed the Bonneville instead of the LeMans in 1981.
H Special (HS body) - 75-80: RWD Starfire/Skyhawk/Sunbird/Monza
H - 85-Up: FWD Bonneville/Delta 88/LeSabre

Pontiac introduced their H-body, the Bonneville, in 1987.
J - 81-Up: FWD Firenza/Skyhawk/Sunbird/Cavalier/Sunfire/Cimarron

K - 85-Up: FWD Seville
K Special - 84-Up: FWD Deville/Concours

L - 87-96: FWD Corsica/Berretta

M - 85-Up: FWD Chevy Sprint/Geo Metro

N - 85-Up: FWD Calais/Somerset-Skylark/Grand Am

P - 84-88: Fiero
97-Up: Electric - EV1

P-90 - 97-Up: FWD Malibu/Cutlass

R - Geo Spectrum/Storm

S - 84-Up: Chevy Nova/Geo Prizm

T - 74-85: RWD Chevette/T-1000

U - Lumina APV/Silhouette/Transport

V - 87-93: Allante
97-Up: RWD Cadillac Catera

W - 88-97/98: FWD (GM-10) Cutlass Supreme/Regal/Grand Prix/Lumina
97/98-Up: FWD (MS-2000) Intrigue/Monte Carlo/Grand Prix/Century/Regal/Impala

X - 62-79: RWD Nova/Omega/Ventura/Apollo/Phoenix (also the original RWD
Seville)
74: GTO
??: F-85, Skylark
80-85: FWD Omega/Skylark/Phoenix/Citation

When this small Cadillac was introduced in 1975.5, GM made so many changes to the 'X' chassis that they gave the Seville a K-body designation (GM's K-car !). The 'K' platform remained a separate entity until about 1991. If I remember correctly, it was amalgamated with the 'C' cars in '92. The K-cars had much in common with '80 and up E-cars.
Y - 53-Up: Corvette

Z - 58-69: Corvair
90-Up: Saturn

GM Trucks:
C - All: Full Size 2WD Pickup
Dn-87: 2WD Blazer/Jimmy/Suburban/Crew Cab
92-Up: 2WD Tahoe/Yukon/Suburban/Crew Cab

G - All: Full Size Van

K - All: Full Size 4WD Pickup, including Blazer/Suburban/Crew Cab except 88-91
Dn-87: 4WD Blazer/Jimmy/Suburban/Crew Cab
92-Up: 4WD Tahoe/Yukon/Suburban/Crew Cab

L - 91-Up: AWD Astro/Safari

M - 85-Up: 2WD Astro/Safari

P - Delivery Van

R - 88-91: 2WD Blazer/Jimmy/Suburban/Crew Cab (old-style body)

S - 82-94: 2WD S-10 Pickup/S-15 Pickup/S-10 Blazer/S-15 Jimmy
95-Up: 2WD S-10 Pickup/Sonoma/Blazer/Jimmy

T - 82-94: 4WD S-10 Pickup/S-15 Pickup/S-10 Blazer/S-15 Jimmy/Bravada
95-Up: 4WD S-10 Pickup/Sonoma/Blazer/Jimmy/Bravada

U - 88-96: Lumina APV/Trans Sport/Silhouette
97-Up: Venture/Trans Sport/Silhouette

V - 88-91: 4WD Blazer/Jimmy/Suburban/Crew Cab (old-style body)

I did not see any one say this.

It is the 4th digit of the VIN.

------------------

quote Originally posted by Leper: H Special (HS body) - 75-80: RWD Starfire/Skyhawk/Sunbird/Monza H - 85-Up: FWD Bonneville/Delta 88/LeSabre Pontiac introduced their H-body, the Bonneville, in 1987. J - 81-Up: FWD Firenza/Skyhawk/Sunbird/Cavalier/Sunfire/Cimarron

Just a quick thing to check. The H RWD Starfire/Skyhawk/Sunbird/Monza should go to 1981 and the J body should start at 1982.
The first year of the FWD J bodies was 1982.

Soo..... we have P-body cars?

Man... why can't we have a cooler letter.