Wood was used because car bodies were an evolution from horse-drawn coaches. Fisher Body was the body-building division of GM.....Fisher originated as a coach builder. The
bodies were originally a wooden skeleton that had thin sheet metal over the wood and the sheet metal was literally nailed in place. As the process evolved, the body became more metal....remember that the stamping press technology didnt allow an entire roof stamping until the middle or late 1930's.

GM was Fisher Body based. Ford didnt have the coach building background but they had stamping capacity so Ford developed wood substitute bodies before Chevy. (also GM had huge forging capacity and Ford had casting capacity so GM had more forged parts than did Ford)

Wood was still used in the steel framed bodies but not as a structure. Rather, the wood allowed the interior to be tacked in easily...remember that the interior people were essentially upholstery people. If you've ever taken an old car apart that was 100% steel, you'll remember the difficult fasteners that were used to hang the interior onto the metal....

Wood worked well for the short term. It probably helped prevent the rattles on the early roads plus it was a good sound deadener.

mike in tucson