The image above shows the top of the center column of the Universal mixer's Slicer Shredder attachment. It illustrates how the Drive Piece can be removed from the top of the Drive Shaft. The Drive Piece is shown lying on its side on top of the Drive Shaft and the Fixed Gear.
In this photo, only the threaded top end of the Drive Shaft is visible. The Drive Piece can be removed by holding the lower, flattened end of the Drive Shaft (under the bowl) with a wrench so it can't turn, and then turning the Drive Piece counter-clockwise. It may come loose by hand turning. If you need to use a pliers on the Drive Piece and if you plan to reuse it, it must be protected from plier jaws to prevent damage. Wrapping it with a piece of leather or dense cardboard will work.
If you wish to remove the drive shaft entirely to replace your bowl, you put a screw driver in the bottom of your Slicer/Shredder bowl and push it side ways. This pops the whole shaft and gear (pictured) out the top of the bowl, ready to pop down into the new bowl.
It may appear that the Drive Shaft could be removed by removing the CirClip from the bottom end of the Drive Shaft. This cannot be done, however, because the flattened end of the Drive Shaft is wider than its shank, preventing it from passing upward through the stainless steel Washer