So after replacing the outhaul gearbox destroyed during our effort last year to remove the "drive shaft" I was most careful top apply anti-sieze grease. Even so I could not remove the shaft with "modest" pounding from below. the solution that ultimately worked was the application of a 4T "bottle jack". Picture attached. Even so quite a bit of pressure was required with the ultimate release achieved by driving screw driver wedges just under the top of the shaft. A caution would be to be sure to fill in the space between the gear box and the boom to transfer some of the pressure to the boom and off the bolts and gearbox top. We used catalog pages to fill the space.
Rock Hall, MD