I read the same ^^^^^ high quality u-joint's usually don't have grease fittings because they don't tend to lose grease. And the fact it adds a fracture point in the geometry. I too have rpm induced vibration in my drive line. Changed axle bearings, trans mount, checked run out on tailshaft, etc... got better after removing stock rubber trans mount with a urethane one, as I'm pretty sure the solid engine mounts with the soft rubber trans mount was an outlet for the vibration... anyone else have ideas? Seems there's a lot of posts here with different culprits for the vibe.