I have a 14 Rubi JKU with a Zone 3" lift. I recently noticed when looking at the Jeep from the rear, it appeared to be leaning to the passenger side. When the lift was installed almost 4 years ago everything was level. I took a few measurements and the back right corner of the body is about 2" lower than the left. Measurements I took were as follows:
front bumper, left and right corners = equal
top of front wheel wells = equal
rear bumper, left and right corners = right side 1.5" lower
rear fender bottoms = right side 1.5" lower
Rock Rails (rear) = right side 2" lower
rock rails front = right side between 1 and 1.5" lower
rear spring heights = equal
rear shock mount (bottom of mount to ground) = equal

I took a look at all the suspension parts and everything appears to be connected and straight. With both springs being the same height I'm eliminating spring failure. Could the body have somehow shifted off the frame? Any other suggestions of what to look at before I have to take it in to a shop?

 

Try measuring the length of the rear shocks, see if the right rear is compressed ~1" more than the left rear. If yes, the right rear spring is sagging -- I think it's more accurate to measure at the shocks rather than at the springs themselves.

 

There is less than 1/2" of difference between the lengths of two shocks, with the right side being the shorter of the two. For what it is worth, I only have 1/2 a tank of gas. I know the "Lean" is common in the JK but 2" seemed a little on the extreme end of what I could find.

 

Try measuring from the body to the frame at multiple places, left and right side, and compare. Might be a combination of some right spring sag and something body related. Maybe swapping the rear springs, putting the stronger one on the right will make it acceptable. The measured lean gets greater the further away from the center of the vehicle, so 1/2"at the shocks might be something like 3/4" at the fenders.

 

Keep in mind you have a 22 gallon gas tank on the passenger side. You could install some leveling pucks if you wanted to even it out more. Some spring sag more than others....and that side is where a lot of weight is.