Universal joints are mechanical couplings that connect two rotating components that meet at different angles. These joints consist of a yoke on each side connected by a crosspiece, known as a trunnion. Cups at each end of the trunnion contain needle bearings which provide a smooth transfer of the torque load, and snap-rings, either inside or outside of the bearing cups, hold the assembly together. Wear in the needle roller bearings can be identified by vibration in the drive line, noise during acceleration, and in extreme cases of lack of lubrication, metallic squeaking and ultimately grating and shrieking sounds as the bearings disintegrate. To check if the needle bearings are worn, one can try to turn the shaft with one hand while holding the rear axle flange or the front half coupling. Any movement between the driveshaft and the front half couplings, and around the rear half couplings, indicates considerable wear. Another method is to use a pry bar inserted into the gap between the universal joint and the driveshaft or flange. Leaving the vehicle in gear and trying to pry the joint both radially and axially can reveal any looseness. A final test for wear is to attempt to lift the shaft and note any movement between the yokes of the joints. If any of these conditions exist, it is recommended to replace the universal joints with new ones.