I'm assuming you are not trying to make a racing mini game in Vam.
If you are trying to get a car rocking due to the activity in the back seat, there maybe a few ways to fake it. You could add two versions of the car in the same spot, and turn the collisions off on one, and use DemonLords DLUtils to hide everything but the wheels. Then on the one for the main body of the car with collisions on do the opposite and hide the wheels. Set its position to on, and Parent it's rotation to another atom (like an invisible capsule shape with physics on placed behind the action.) Use the physics interaction between the characters and that atom to drive the movement of the suspension. I've not tested, and It would take some tweaking to look good, but that would probably get a car rocking.
Basically this plugin gives some abilities from Unity Editor. Add plugin to builtin asset or CUA or Light, change parameters as you want. DLUtils plugin can: Edit builtin assets or CUA: - turn off All GameObjects - turn off All...
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