There's a cork seal ring under that nut. You can try tightening the nut to see if it slows down, or there are reseal kits for the u-joint ball, but you have to pull the whole thing off the end of the driveshaft to replace it. It's not a real easy job, as you have to either jack the torque tube up above the transmission housing (assuming there's enough room between it and the cab floor or drop the transmission mount crossmember (you might not have one on a '53) to drop the torque tube below the transmission. You also have to select the number of gaskets that go between the transmission and ball housing before installing the cork seal at the ball. The service manual covers the procedure.
I would try snugging up the nut first. That might slow it down to a smaller drip. You also need to be sure that the u-joint housing is filled with gear oil thru a side plug near the rear. If it stops leaking by itself, that means the u-joint isn't being lubricated and might blow up on you.
