Im having the same problem right now. Anyone know the trick to get it off?
There is a sleeve or wear wear ring/collar over the end of the crank. It must be removed before the oil pump gear will come off. If you look at the new front seal set it will come with a new wear sleeve. You are suppose to use special tools to remove the old sleeve and install the new sleeve/seal. I made my own special tools to press the sleeve on..... 2k+ miles so far and no leaks yet.
02' Ford Lightning---- twin turbo'd
08' King Ranch F250 - egr/dpf deleted; tuned