Not if all you have is a metric crescent wrench. :D
If I had a ujoint making noises like the OP described it would get fired and I'd hire a new one, not grease it.
Well ok, I might grease it to get a couple of days out of it till I had a new one/two ready to go in.
Oh and to the OP, a ujoint generally makes noises that are about 3-4 times faster than the tires turn.
Also another dead giveaway is if the driveline goes CLANG! with and automatic trans when put in gear or shifted from forward to reverse, or vise versa.
Just for future reference.