in Unity 3.5.7 car starts to shake

Hi

I upgraded to Unity 3.5.7 today. one of the problems that came with it is,the car starts to shake when I start to go ahead. I use the script from the unity car tutorial so the script should work properly because unity made it! I use the GMC car for physics with the CarControler and the Drivetrain script,

what happens is the car worked well in unity 3.3 but with 3.5 it starts to shake when I move then even starts to bounce around.

anyone had this issue with the newer unitys?? does anyone know how to fix this problem? I think its something with the wheel not contacting with the ground well.

thanks ahead :)