You should crawl under the front and shake the axle U joints. There should be zero play in the joints. Put a glove on and check them for any play. If you feel play, replace the u joint.
I see you have the RE kit. The johnny joints on the RE control arms are notorious for binding. The UCA joint is at the rear of the UCA. If the left one is binding, you can feel the popping through the floor on the drivers side. I have this problem on my rig right now and am waiting for the brown santa to show up with the RE tool to take them apart. If you haven't heard, RE was bought by Four Wheel Parts a few months back. You can no longer buy direct from RE. You will need these tools to take the joints apart, RE3771 & RE3772.
When I was looking for parts and tools, I called RE (their tech support is still active), Four Wheel Parts and 2 local vendors. As soon as I mentioned Johnny Joints, they all interrupted me with the quesiton "have you loosened them?" The RE rep admitted that in the past, they were setting the joints too tight before they were shipped. RE also told me any grease was acceptable, it was only there to prevent dirt from getting into the joint. One of the vendors explained they used to pull the collars all the way down until the ball could just be rotated. He said they now back the collars off one quarter of a turn before locking them with the setscrew.
If you decide your problem is a binding johnny joint, drop the control arm, taking all the usual safety precautions and only disconnedt one side at a time. You should be able to easily rotate the ball inside the joint with the attaching bolt. If it is binding, time to open it up, clean, lube and adjust the joint.