hi everyone! does anyone know how to make a roller chain or an engine belt with teeth on it in 3D using autocad 2008? thanks guys i do appreciate if you could answer me right away 

Got to the following site and you should find all that you need.  Mr. Bliss has quite an array of inventor stuff already created.
 
 
http://www.cbliss.com

Yes, Autodesk Inventor is definitely much more suitable for such tasks.

ok thanks! but is there a way that i can do it in autocad?

The only way I was able to do it was to take all the measurements for all the pieces of the chain and the manually draw them and the start putting together the pieces.  I only had LT 2000i to work with so if you would like me to send you the file let me know.
 
 

You can start with the 3D model:
http://www.cadforum.cz/catalog_en/block.asp?blk=2287
as an inspiration...