Is there a particular reason for vehicles to behave completely incoherently when colliding with other vehicles? I have a fully working vehicle in a (more or less) final state. Handling and performance are fine but there’s no way to get a decent collision response on vehicles. Crash at 200km/h on a stationary vehicle and it doesn’t move as if it is a concrete wall. Touch it at 2km/h and it starts jumping around at light speed. This is completely reproducible with the default UE vehicle template. Just drag a couple of vehicle in the map and try to hit them with your car. I mean, come on, this is basic stuff. Did nobody test it?
What you are having + some other issues with vehicles are known by Epic and are being worked on by both Epic and Nvidia. You can read the whole story here: Horrible Car Physics - Feedback for Unreal Engine team - Unreal Engine Forums