Mini-Z MR-02 Precision Ball Differential Shaft KYOSHO MZII-003 by 3Racing  [MZII-003]

Technical summary of the MR-02 differential shaft

This shaft is a service replacement intended for KYOSHO Mini-Z MR-02 MM and RM ball differentials. The MZII-003 serves as the rotating axle within the differential cage and is intended for routine maintenance or repair work on electric micro touring cars used in competitive or club environments.

Fitment is limited to Mini-Z MR-02 (MM) and Mini-Z MR-02 (RM) chassis; confirm your variant before installation. The component secures the bearing stack and transmits torque through the ball assembly, influencing slip characteristics and delivering repeatable drivetrain response when the rest of the differential components are within spec.

Installation guidance: extract the differential housing from the transmission case, remove the worn shaft and bearing pack with care, then orient and install MZII-003 into the differential cage. Reuse serviceable ball bearings and shim stacks or replace them if wear is evident. Verify differential preload and axial play using the tolerances given in the MR-02 service documentation and perform final checks on a clean bench with precision hex tooling.

Setup considerations: shaft replacement restores the mechanical datum of the differential, but tuning remains governed by ball grease viscosity, shim geometry, and preload calibration. Address ball condition and lubricant choice during a shaft swap to maintain consistent lap-to-lap behaviour on micro touring surfaces.