Thanks for your help! Now I know I do not want the Redcat diff . I prefer the kit in this link because it seems better built and has some extras parts that I can use for this project!
http://www.ebay.com/itm/FS-1-5-RC-BU...item5ae000b43c

What do you think about this kit?
To me it seemed to me excellent and comes equipped with the transmissions for front wheels