Pete if you have snapped it you might want to look into a stronger replacment such as a titanium version when i used to have my b4 I snapped 3 rear ball studs so i replaced them with titanium versions with no problems at all.
I use losi titanium .388 part number A9947 avaliable from DMS racing just type the part number in the search...
http://www.dms-racing.com/
A