What I did on my pump is, using a punch I drove the sealing ball bearing that is staked in place in the pump right out. I then enlarged the diameter of the drilled passages. Then to re-seal the passage again instead of another ball bearing, I drilled and tapped for a 1/8 pipe plug. The diameter of the fluid passage for high gear is very small in the 904. Be careful not to enlarge the passage too much or your drill will break through the two ring sealing grooves. Mine just barely did this but did not affect its operation once the drum is on. Do at your own risk lol.
