Could be several things. It could be the other axle shaft. Chances are if one is bad the other is as well or is shortly behind. Have someone site in the center in the rear and listen for the noise, you might be able to pin point which side is making the noise.

Also, check your sway bar links. They can make odd noises. They are simple to remove. Just need a 17mm(I think) end wrench. If the boots are torn or missing they are toast. If you pull them off. The ball joints shuold be hard to move, if then are loose or floppy then it's time for a new one. Also make sure the exhaust isn't hitting anything. Give it a good wiggle and see what happens.

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