I have a 1999 jeep cherokee 4.0l and their is a clicking?

[wocketsdrums]

I have a 1999 jeep cherokee 4.0L and their is a clicking coming from under the car. From what I can tell it is the rear left wheel, I have recently replaced the transfer-case so little chance it will be that. I also thought it was the front U joints, but I am unsure. When I am under the car at the engine while it is running I do hear a noise where the exhaust is going up towards the engine?