S&S’s Gear Drive kit for Twin Cam® engines replaces the factory cam chain drive with inner and outer gear sets.
Zip Tip Regarding Gear Drive Usage – Crankshaft run-out must be measured before the installation of gear drive gears. Because gear mesh is set to tight tolerances on gear drive systems, it is important that the total crankshaft run-out at the end of the pinion shaft be no more than .002” when installing gear drive gears. Run-out in excess of .002” can cause failure of the gear teeth of the gears due to the pinion gear oscillating with an out-of-spec crankshaft. Refer to H-D® Tech Tip # 324, 8-22-07 for instructions on how to measure crankshaft run-out (use tool # 772-015 to simplify measurement). Over- or under-size gears should NOT be used to correct an out-of-spec crankshaft problem.