Originally Posted by cherry2blost

I found that the Yokomo BD4 diffs work exceedingly well (and are fairly indestructible). they are a 40 tooth pulley in place of the 39 for the Cyclone, but by using the 17 tooth pulley from the 3Racing kit along with the amended belts for the 39/18 arrangement you get a nice smooth drivetrain with just the right amount of tension but with a easy 2.353:1 ratio.

This is what I use and works a treat (fed up with HB diffs melting)