U joint

Signs of wear in a universal joint (U-joint) on your 4x4 become apparent through noises. It starts with a faint humming noise, which eventually escalates into a loud and sharp clunking sound. These sounds are accompanied by increasing vibrations and knocks when you apply power to your 4x4's engine. The diagnosis is confirmed by getting underneath the 4x4 and manually manipulating the driveshafts (or prop-shafts as often referred to). At this point, it's essential to replace the faulty U-joint.