That slop in the rear diff is just that, slop. Its not what is making this popping sound. Focus on the popping noise. Dont create problems that aint really there. It might be time to find a trustwodthy mechanic and take him for a drive, make it make the noise, and see what he thinks? If its as loud and scary as you described, its only going to get worse and reveal itself... eventually... Probably sooner than later.
My apologies, I wasn't asking about the slop to go down a rabbit hole. It was just a question. I am still trying to pinpoint the noise. Last night was the first time I clipped the gopro to the a cross sill of the bed and took it for a drive. It's a little limited on where it can be pointed as it doesn't swivel. To start off I pointed it at the rear end. Took it for a drive, and it did pop, not a big loud one, but it did pop, twice. Unfortunately it wasn't apparent in the video when it happened. I have to dress nicely for my job, so crawling under the truck before and during work to mount the camera is not good at staying clean. However, I brought the camera with me today along with an old sheet to lay on the ground so I can mount it pointing towards the trailing arm-to-frame connections next.
