where can i download automotive 3D designing software ?

its right after the page that asks for credit card info and $3,000 US.

if you work at GM you could try to get it for free.
just make sure you have your things packed up first.

You can buy a student version of Alias AutoStudio 12 at Academic Superstore fro $149.95.

is there any free ones?

Not for automotive, at least nothing worth using.

149 is an amazing price!