Kyosho IF103B Differential Case Inferno MP777

This is the differential case for Kyosho's Inferno platform, the housing that contains the diff gears and the silicone oil they run in.

The case does two jobs at once. It locates the internal bevel gears in correct mesh with each other, and it seals the oil in. Both matter equally. A case that is worn or distorted lets the gears run out of true, which chews the tooth faces, and a case whose sealing surface is damaged lets oil weep out past the gasket. That second failure is the more insidious one, because the diff progressively loses the viscosity you set it up with and the car just starts diffing out more under power without anything looking broken.

Cases also wear internally where the outdrives pass through them, and once that opens up you get play in the whole diff assembly.

This is the B revision, which supersedes the original IF103 and is Kyosho's current supply. Dealers list the pack as the case plus a gasket. Kyosho lists the original for the Inferno MP-7.5, MP-777 and Inferno GT, with dealers adding the GT2, ST-R, Inferno NEO and the USA-1 and Mad Force monster trucks.