To use a hydraulic press, first place the crank shaft gear on the shaft. Then, place the hydraulic press on top of the crank shaft gear and apply pressure. The pressure will force the crank shaft gear to fully seat on the shaft.
To use a hammer and drift punch, first place the crank shaft gear on the shaft. Then, use the hammer to hit the drift punch. The drift punch will force the crank shaft gear to fully seat on the shaft.
To use a heat gun, first place the crank shaft gear on the shaft. Then, use the heat gun to heat the crank shaft gear. The heat will cause the crank shaft gear to expand and this will allow it to fully seat on the shaft.