Why does my car shake really bad going past 40? And you can hear every bump?

SWAY BAR END LINKS MIGHT BE BAD

Possible problem with suspension, wheel bearing or brake rotors. Need to have inspection to be sure. Have you ever had the motor mounts changed? These are an issue on PT Cruisers.

could it be the axles

I have an '04 PT GT, I have the same issues. It could be a number of things though. I know for a fact that my tires are out of balance as the front tires need to be replaced, just haven't got around to doing so. The passenger side tire took on uneven wear from a bad wheel bearing and the rear tires are just about new. So I did a tire rotation for the time being to use the better tires as my drive tires. Now in the back its shakes and bounces after 40+ MPH. the shaking has only gotten worse and I have a feeling the bad tire caused excessive wear in the rear hub assembly bearing. But if your vehicle sounds like it is popping after hitting a bump, you could have a bad shocker absorber on top of a possible unbalanced tire.