HUBS! The auto lockers can be tricky, though. If a hub is failed and stuck into the locked position, it can actually cause the other hub to try and lock in, causing a noise on the GOOD side. It took me a while to get that figured out. I finally upgraded to manually locking hubs, and will not be looking back.
The other possibility is the center link binding with the UCA mount. Do you have any kind of lift? Especially with a lifted truck with the stock center link, the increased angles of the tie rod and tie rod ends can add a vertical force to the center link. This can cantilever it upwards, and cause the tie rod end/castle nut to bind with the upper control arm mount/frame area. This can cause a tight turning feel as it get's stuck, and popping noise as it forces it's way through the interference. The only fix for me was a grassroots4x4 center link.