It's very easy to identify if you have a bad Jeep JK ball joint, the first signs will be a cranking or squeaking sound caused when your Jeep suspension system moves up and down, especially when you hit the trails, or when traveling on rough surfaces. The cranking or squeaking voice will be caused by the ball joint rubber boot that protects the grease inside the ball joint, when the rubber boot is worn out the grease will wear off and the ball joint will start to squeak when in contact with the ball joint socket.