I have a Murray riding mower and am trying to take the rear wheel off to put it on another one that i am switching everything to and the pin has been pushed down too far. Have tried grease, wd40 and crow bar and hammer. But nothing will loosen it. Does anyone have any suggestions on what i can try?

If your wheel is attached with a single bolt into the axle this may help. Leave the tractor on the ground and back out the bolt about 3 full turns. Put a block of oak on the bolt and smack it smartly with a small sledge or framing hammer. It should pop after a few hits.