Kyosho IF406-43 43T Ring Gear Inferno MP9

A 43 tooth ring gear for Kyosho's Inferno differentials.

The ring gear is the large bevel gear inside the diff that the pinion drives, and together the pair set the internal gear ratio of that differential. On a 1/8 scale car this is a serious load-bearing component: all of the drive to that axle passes through the mesh between two bevel teeth at any given moment, and the tooth form has to stay exact for the diff to run quietly and last.

Ring gears wear, and they fail in a specific way. The tooth faces polish, then pit, then start to round off, and the diff gets progressively noisier under load until teeth begin to strip. Running a worn ring gear against a fresh pinion just destroys the new part, which is why they are normally replaced as a matched pair.

Correct mesh at installation is critical and is set with shims. Too tight and it binds and runs hot, too loose and it will strip under power.

Despite the MP9 name, Kyosho lists this across the MP9 TKI4 V2, MP10, MP10 TKI3, MP10e, MP10e TKI2 and MP9e Evo. V2.