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what makes chevy 4x4's bounce soft to hard while driving down the street. /forums/images/graemlins/dunno.gif
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The same reason double post /forums/images/graemlins/doah.gif If ya ain't liking the answer doesn't mean you have to post the same question twice.
It's all about the spring rates and shock valving. With trucks of yesteryear, manufacturer's threw on springs that were thick and built for for hauling loads. These springs had no flex in them. The shocks were valved to handled these same loads.
Now you see a lot of pick-ups on the roads these days, but the manufacturers realized they were sitting on a goldmine if they made them ride more like cars.