When we rebuild a LT 230 we use the later cross drilled input gear to stop the spline wear problems these boxes suffer from, This gear is not only cross drilled but also the internal spline length is longer. If you are changing a LT 230 for a later one with this cross drilled gear you will also need to change the corresponding ZF Auto coupling shaft for this FTC5090 which has a longer male spline to suit this gear.