are you sure that you used this code? I use this code in a car simulator and it works perfect

Code:
var camera_distance=30;
camera.x = chassis.x - sin(chassis.pan) * camera_distance;
camera.y = chassis.y - cos(chassis.pan) * camera_distance;
camera.z=chassis.z+10;
camera.pan = chassis.pan; // face the player


3D Gamestudio A8 Pro
AMD FX 8350 4.00 Ghz
16GB RAM
Gigabyte GeForce GTX 960 4GB