After turning off the power to the blender, there are at least three techniques you can use:
1) Use a (very thin) 7mm spanner to hold the drive shaft directly under the rubber coupling. You should be able to unscrew the old rubber coupling clockwise (i.e. opposite to normal)
2) Use an old screwdriver to bash the coupling teeth, so that the coupling rotates clockwise, as above. Several sharp blows will be required. The inertia of the heavy motor should be enough to prevent the drive shaft rotating very much during this process.
3) Use a screwdriver inserted between the base and coupling to progressively prise the coupling upwards. Be sure to clean away any aluminium swarf left on the threads of the drive shaft.
Ref:http://www.2mro.co.uk-a.googlepages.com/kitchenaidblenderrubberclutchcoupler9704
Geoff Hodges, February 2009