I have a 2005 FD1 Honda Civic and the whole gear box needs to be rebuilt due to the input shaft bearing collapsing, what causes this?

I have a 2005 FD1 Honda Civic and the whole gear box needs to be rebuilt due to the input shaft bearing collapsing, what causes this?

Racing. Constant running at redline.

Besides proper lubrication, the causes are typically due to a worn pilot bearing causing an un-centered load, or faulty installation of the isb on rebuilt transmissions. Driving it hard under those conditions leads to premature failure.

Not having transmission oil in the tranny