Spreader New Idea #81 Drop spreader wheel removal

[Barneyhunts]

I recently purchased a New Idea model 81 drop spreader and the spreader needs new tires. In order to remove the wheels it appears that I have to remove the device that allows me to engage or disengage the agitator drive. The device is on the axle outside of the wheel and it appears to be held in place by a cotter pin and washer. Does anyone have any experience with this spreader & device? I've removed the cotter pin and washer but I cannot pull the device off the shaft by hand, and I don't see how I can grap it with a puller.
Thanks for any help,
Jack