I'm freaking shocked how hard it was to find what a chassis is, and the best answer is this video... They don't make em like they used to... Gosh darn heros, whoever made this, Thank You!!!
Man, they really did used to over build cars back then with those heavy duty frames, unlike the newer cheap plasticky unibody vehicles of today. A unibody vehicle just can’t deflect harsh vibrations from the road like potholes, or even rough surfaces nor ride as smoothly like a body-on-frame chassis does. A lot of people don’t understand that back in the 1920’s-1950’s, a lot of Americas roadways were still actually unpaved dirt roads in many parts of the country. So all the cars had to have a full frame in order to take the severe punishment of the uneven rough dirt roads that many of those old cars had to endure. A unibody vehicle would have split in half (just kidding lol) or would flex way too much driving on dirt roads like that which would possibly damage the body with stress cracks and broken windows around the A-Pillars and C-Pillars.
As always, it depends what unibody from when. The modern ones are obscenely stiff because of crash test requirements. Certainly a lot stiffer than a 60s, 70s, or 80s GM body-on-frame. I have seen an old dodge b body with plenty of stress cracks like you describe though. Hell, the E-type had a sort of hybrid thing going on where it was a unibody right up until the bulkhead, then a bolted on tubular spaceframe front. As the video puts it "the stress was localized"...
So what if newer cars don't have a frame look at all the money they saved when they stopped building cars with frames. No they are not safe but look how much money they saved. If they can just start building houses with no foundation look how much money they could save. IT'S Not about safety it's all about money. MORE MONEY.
These old cars were death traps. The frame was only underneath the floor and couldn't stop the passenger compartment from being crushed if someone hit you. The bodies were very very weak, only expected to hold their own shape and no more.
