Hey BUBB, welcome!

This is the HPI clutch bell you need - http://www2.towerhobbies.com/cgi-bin...?&I=LXFKM8&P=7


It's the 18t, rather than the 16t stocker. It will add more top end speed, and you won't lose much torque at all. You can get any size you want, as far as teeth, just make sure it's the $11 version for the HPI Savage, which is the H/D (heavy duty) hardened steel. The $6 one is just as bad, if not worse then the stocker. You'll also see the racing ones for about $15. You can get one for the cool factor, but it's not necessary. Compatible, but not necessary... These are direct replacements. No mods or extra parts necessary.

Like I said, HPI Savage H/D or Heavy Duty 18t. If you don't want to get it from Tower, the HPI part # is A993. I was lucky enough to find it at one of my LHS (local hobby shops)