try tightening it first to break the threads loose. Sounds crazy...but sometimes it works

Its only steel anyways, you want to be careful with it, but a small mini torch heating up in bursts might work too...don't let the flame stay longer than 10-15 seconds on the area, the threads in the UCA are very few and you might do harm to them.

Mine was a 3/4" drive as well....Cover your knuckles with gloves and a few rags otherwise you will be for a few hours