Kyosho IF102 Differential Bevel Gear Set Inferno

This is the internal bevel gear set for Kyosho's Inferno differentials, and it works in the front, centre and rear diffs.

These are the gears that actually make a differential differentiate. The two outer bevel gears connect to the output shafts, and the smaller spider gears between them rotate on a cross pin, allowing the two outputs to turn at different speeds while still both receiving drive. Every bit of torque going to that axle passes through the mesh between them.

Because a gear diff on a 1/8 scale car is filled with heavy silicone oil, the gears also work against significant resistance all the time, not just when the wheels are turning at different speeds. That is what wears them. The tooth faces polish, then pit, then start rounding, and the diff gets progressively noisier and less positive until teeth begin to fail.

Replacing them as a complete set matters, because a fresh gear meshing against worn ones just destroys the new part. Dealers list the set as two outer bevels plus four spider gears with shims. Kyosho lists fitment for the Inferno MP-7.5, MP-777 and Inferno GT, with dealers adding GT2 and ST-R.