[Crayder]

CheckVehicleGroundContact could be drastically improved. The point of it is to check if the wheels are on the ground, but it doesn't. You are already getting the vehicle's quaternion rotation so why aren't you using rX and rY in the CheckVehicleGroundContact function? With that you could easily get the actual wheel position of each wheel and cast rays from the tires away from the bottom of the vehicle (in the actual direction it they should be going)! Plus, this way you would only need 2 or 4 rays, and if those don't detect the wheels on the ground you can check for the rest of the things (in GCRayMatrix).

Other than that, I love it.