Case 580B frozen differential sprocket

First and foremost let me apologize as I am sure this has been posted, probably numerous times before. Because I am new to not only this site but this machine (and any backhoes) I hope you will excuse me for asking it one more time. I have a 1975 Case 580B construction king. The right tire is frozen and so after reading numerous posts I have decided to take off the brake and the differential and replace parts. The problem is the differential gear is frozen on the sprocket and I have tried everything (I can think of) to get it off and I’m looking for any suggestions or help. I know it is supposed to just slide on and I’m sure it did 47 years ago but at this point it will not slide off. Any suggestions or help would be greatly appreciated. Couple photos posted to assist, you can see, not only my luck to not get it off but then it started raining… part 20 is frozen on part 39. Thanks for your time and consideration for assistance.