1937-1938 General Motors A & B Body 4-Door Sedan Comparison

According to Michael Lamm and David Holls (here, page 97) General Motors' shift to multi-brand body platforms began in 1931 from an analysis of current production bodies by Vince Kaptur.  This took a while to implement, but was in force by the 1936 model year for all GM cars, perhaps aside from luxury vehicles.

Factors that brought this into play were the Great Depression that resulted in fewer sales and less income as well as the shift to all-steel bodies that required more expensive production tooling.

Platforms were designated by letter.  The link above states:

"Harley Earl showed Kaptur's conclusions to Fished Body and suggested that all GM cars share four basic body shells.  He designeted these A-B-C-D.  The A-body would be used by Chevrolet, standard Pontiac and small Oldsmobile.  The large Pontiac, mid-size Oldsmobile and small Buick would use the B shell.  The C-body accommodated the big Olds, big Buick, LaSalle and small Cadillac.  And all Cadillac and Buick limousines used the D body."

That was the concept, but details varied over time.

Wikipedia has entries dealing with the bodies dealt with in this post: A platform here; B platform here.  At this time I drafted this (February 2024), some details did not agree with Lamm and Holls, who I am more inclined to trust regarding certain dates.

I lack charts of body dimensions, so the analysis below is simply based on study of photos.  More precise information is greatly appreciated.

All but one of the images below are of for-sale cars.

Gallery

1937 Chevrolet Master DeLuxe
All 1937-38 Chevys had A-bodies.

1937 Pontiac DeLuxe Six
Another A-body, perhaps, but note that the C-pillar is vertical and not slanted, as seen on the Chevrolet in the previous image.

1937 Pontiac DeLuxe Eight
Wikipedia does not mention the body for Pontiac Eights, though theoretically this is a B-body.

1937 Oldsmobile F-37 Six
Another A-body, according to the plan mentioned above.

1937 Oldsmobile L-38 Eight
Eight cylinder Oldsmobiles had B-bodies.

1937 Buick Special
Fastback B-body variation.

1937 Buick Century - Mecum Auction photo
B-body on a longer wheelbase.  As you might have noticed, passenger compartments for B-bodies and non-Chevy A-bodies are quite similar.  They might even share a good deal of the structure and sheet metal stamping.

August 2024 note: That C-pillar difference starting with the Pontiac Six bothers me.  I have the nagging feeling that all cars with that feature are actually B-body examples.  Is there any source that explains strong visual similarities between non-Chevy A and B bodies?  Or was Chevrolet the only user of A-bodies in those days?