U joint help

[gman]

Have a god awful clunk noise when releasing the clutch. If I release it extremely slow, i can prevent it. But just drivng it normally, it sounds like hell.......like its going to break. I'm assuming its u-joints but I'm not sure. How do I diagnose where the problem is? The u-joints at the back differential, at the front of the transfer case and the rear of the tranny all have zerks on the inside of the joint and are so cramped I can't get a grease nipple on them. Are the non greaseable kind the way to go if the u-joints need replacing? Any wisdom appreciated. Thanks!