If you are trying to swap the coupler from one shaft to the other and the coupler won't slide off there is probably a roll pin inside that is stopping it. Wipe some of the grime off that thing and you will see a small hole near the top of the coupler on one of the sides. Pop the top cap and grease seal off the top of the coupler and you can usually use a pair of channel locks to GENTLY push it out. No need to completely remove it just don't bugger it up.