I'm not sure it's even assembled correctly - there is a metal washer (pretty loose around the torque tube), cork gasket (pretty tight) then another metal washer, then the screw-on collar. I am wondering if that is correct. And if so, I would like to seal it without breaking the U-joint apart
your description is correct
If your install a new seal the leak may slow down and might even stop.
You do have to take the u joint apart to replace the seal.
I guess your asking if you could just add some packing (or similar) around the tube to stop the leak.
Good Question
I once thought about backing off the collar nut and adding rope packing, (like in a valve gland) Ended up going with a new seal.
My leak did not completly stop with the new seal. It did get alot better
Good Luck